influence the. Application techniques, including field dosage, volume, irrigation and ...... however, the second generation eggs do not hibernate and hatch within 11- ...... Guwahati. www.apiindia.org/pdf/medicine_update_2017/mu_008.pdf. 51.
LATEST TRENDS IN ZOOLOGY AND ENTOMOLOGY SCIENCES Volume - 6
Chief Editor Dr. B.S. Chandel (M.SC., Ph.D., D.Sc., Zoology (Entomology), Associate Professor and Head Department of Zoology, Entomology, D.B.S.P.G. College, Kanpur, Uttar Pradesh, India
AkiNik Publications New Delhi
Published By: AkiNik Publications AkiNik Publications 169, C-11, Sector - 3, Rohini, Delhi-110085, India Toll Free (India) – 18001234070 Chief Editor: Dr. B.S. Chandel The author/publisher has attempted to trace and acknowledge the materials reproduced in this publication and apologize if permission and acknowledgements to publish in this form have not been given. If any material has not been acknowledged please write and let us know so that we may rectify it. © AkiNik Publications Pages: 145 ISBN: Price: ` 595/-
Contents
Chapters 1. Subterranean Termite and Their Associated Fungi
Page No. 01-15
(Yasmeen Shaikh, Gulfisha Shaikh and Shivaji P. Chavan)
2. Entomopathogenic Nematode a Potential Tool for Biological Control of Insect Pests
17-33
(Saroj Yadav and Jaydeep Patil)
3. Biological Control of Insects by Birds
35-46
(Nagamandla Ramya Sri, Nagulapally Sneha Latha, Gautam Kunal and Pavan Thakoor)
4. Pesticide use ill Effects in Relation to Invertebrates and Vertebrates
47-68
(Nagamandla Ramya Sri, Nagulapally Sneha Latha, Gautam Kunal and Venisetty Punnamchander)
5. Sericulture
69-103
(Zafar Iqbal Buhroo, Muzafar Ahmad Bhat and A. Aziz)
6. Status of Dengue Vectors in North Eastern Region of India
105-130
(Momi Das)
7. Status of Whitefly, Bemisia tabaci as Insect Vector and Their Management: An Overview 131-145 (Anil Kumar and Nagend Kumar)
Chapter - 1 Subterranean Termite and Their Associated Fungi
Authors Yasmeen Shaikh Aquatic Parasitology and Fisheries Research Laboratory, Department of Zoology, School of Life Sciences, Swami Raman and Teerth Marathwada University, Nanded, Maharashtra, India Gulfisha Shaikh Aquatic Parasitology and Fisheries Research Laboratory, Department of Zoology, School of Life Sciences, Swami Raman and Teerth Marathwada University, Nanded, Maharashtra, India Shivaji P. Chavan Aquatic Parasitology and Fisheries Research Laboratory, Department of Zoology, School of Life Sciences, Swami Raman and Teerth Marathwada University, Nanded, Maharashtra, India
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Chapter - 1 Subterranean Termite and Their Associated Fungi Yasmeen Shaikh, Gulfisha Shaikh and Shivaji P. Chavan
Abstract In the present study termites and ant differentiation, they have grouped into 6 families, 170 genera and 2600 species. Out of 2600 species of termites 300 species are economically important. They have been classification on the basis of habitat viz. Dry wood, Damp wood and Subterranean. On the basis of their morphology they are classified into two categories viz. Lower and Higher termites. In the lower termite’s six families i.e. Mastotermitidae, Kalotermitidae, Hodotermitidae, Termopsidae, Rhinotermitidae and Serritermitidae and second one is higher termite has Termitidae. Termite biology, life cycle, nutrition and their symbiotic associated with 12 genera of fungus for ease assimilation of lignocellulic materials. Keyword: Termite, Nutrition, Biology of termite, subterranean termite, Fungi Introduction Termites are invertebrate, belongs to Phylum Arthropoda, from largest Class Insecta and Order Isoptera. These are social insects. These insects live in constructed nests of soil, feces and saliva; which are humid environments rich in organic material (Sands, 1969). They are sometimes called white “ants” however they are not ants; hence true ants belong to order Hymenoptera, while termites belong to order Isoptera (Grimaldi and Engel, 2005). Engel and Krishna (2004), termites grouped in 6 families, 170 genera and about 2600 species, out of which 300 species are economically important. Termites can be divided into three general categories based on their habitat: damp wood, dry wood and subterranean (Paul and Rueben, 2005). According to Paul and Rueben (2005), damp wood termites do not present wide spread pest problems, but can be problematic under certain conditions, dry wood termites are significant and costly pests, while the subterranean termites are the major urban pests. They are polymorphic, colonial and social insect. The members of a colony often occur in huge Page | 3
population and they live together in the nest or termitarium, constructed by them. There is a well synchronized division of labour among the members of a colony and sort of language for communication. Their feeding habitat includes decomposition of dead trees and incorporation into the soil, mineral nutrients of these trees. The destructive activities of termites as a result of their feeding habitats cannot be over emphasized. It includes the damages done to agricultural crops such as crash crops and food crops (Harris, 1961; Abe et al. 2000). Timbers are buildings, post, fences, damages to clothes, books underground cabals and air fields, earth dams and irrigation canals. The termites divided into two categories. First one is the lower termite viz. Mastotermitidae, Kalotermitidae, Hodotermitidae, Termopsidae, Rhinotermitidae and Serritermitidae and second one is higher termite viz. Termitidae.
Fig 1: Classification of termites
Classification of Termites Termites can be categorized based on habitat as follows 1) Damp wood termite 2) Dry wood termite 3) Subterranean termite
Fig 2: Dry wood termite, Damp wood termite and subterranean termite (image source: https://cdn.orkin.com)
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1) Damp Wood Termite The damp wood termites Paraneotermes simplicicornis require more wood moisture than provided humidity. Under natural conditions, they are restricted to moist wood in contact with damp soil (Light, 1994). Damp wood termite’s nests in wood burried in the ground are not necessary when infested wood is high in moisture. Hence, they need high moisture, damp wood termites most often are found in cool, humid areas along with coasts and typical pest of beach houses. Winged reproductives typically swarm between July to October, but it is not usual to see them at other time in year. Winged reproductives are dark brown with brown wings. Soldiers have a flattened, brown or yellowish brown head with elongated black or dark brown mandibles. Nymphs are cream colored with a characteristics spotted abdominal pattern due to food in their intestine. 2) Dry Wood Termites The dry wood termites are pests of dry structural lumber or wood furniture. They require no contact with soil and live entirely within their food source (Su and Scheffarahn, 2000). Dry wood termites infest dry, undecayed wood, including structural lumber as well as dead limbs of native trees, shade and orchard trees, utility poles, post and lumber in storage. From these areas, winged reproductives seasonally migrate to nearby buildings and other structures usually on sunny days during fall months. Dry wood termites have a low moisture requirement and can tolerate. They remain entirely above ground and not connected to their nests in soil. They vary considerably in color, but appear granular, salt and paper like in color and appearance. Winged adults of western dry wood termites (Incisitermes minor) are dark brown with smoky black wings and have a reddish brown head and thorax; wing veins are black. These insects are larger than subterranean termites. 3) Subterranean Termite The subterranean termite is most widespread and destructive group. They oblige name subterranean termites due to association with soil. They require moist environments; to assure this need, they usually construct nest in or near soil and maintain some connection with soil through shelter tubes. These shelter tubes are made up from soil with bits of wood or even plasterboard. Much of the damage due to occurs in foundation and structural support wood. Hence, moisture requirements of subterranean termites are often found in wood that has wood rot. The western subterranean termites Reticulitermes hesperus, is most destructive termite found in California. Page | 5
Reproductive winged forms of subterranean termites are dark brown to brownish to black, with brownish gray wings. On warm, sunny days following fall or sometimes spring rains, swarm of reproductives may be seen. Solders are wingless with white bodies and pale yellow heads, along with their long narrow heads have no eyes. Workers are slightly smaller than reproductive, wingless and have a shorter head than reproductive’s, wingless and have a shorter head than soldiers; there color is similar to that of soldiers. Biology of Termite The termite colony is typically composed of four main castes or types of individuals; king, queen, soldiers and workers. The entire population of colony consists of parent’s pair and their offspring. The parents are long lived, may survive from 15 to 50 years, while the offspring are short lived, with life span of hardly 2 to 4 years and this replaced by daughter of succeeding generation. The king and queens of termite colony reproduce, the workers forage and feed their nest mates, and the soldier defends their home colony. Unlike the social Hymenoptera, termite societies contain individuals of both sexes, and they show a larval instead of an imaginal polymorphism. Moreover, lower termites can change their physical caste during development in case of temporal polymorphism (Noirot, 1991). Usually, termites nest contain countless subterranean ducts and chambers and spectacular hill shaped colonies may rise to several meters. Wood living termites inhabit living wood and rotten logs or stems. ‘Lower termites’ however do not form a monophyletic taxon but an ancestral grade composed of a series of families sharing several plesiomorphic character (Noirot, 1991). For cellulose digestion they all depend on intestinal flagellates. The “Termitidae” referred to as the higher termite, are the largest family comprising about three quarters of termite species. Higher termites do not passes symbiotic protozoa in their gut and display a more complex external and internal anatomy and social organization. Phylogenetic trees based on family level relationship inferred from molecular data and from morphological characters differ in some aspects. Symptoms on Infected Tree Many termites will live in small holes and wood shavings; where they have entered within wood. The best place to look for them is around the base of tree; use a small shovel to dig usually exists just below soil. Hence, Formosan termite colonies are so large and may also see discarded wings and termite carcasses. Other signs included shelter tubes on the trunks of
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trees, swarm ‘castles’ located within scars of the trees or even small white eggs. Here some of the signs of termite
Termite shelter tube
Blow holes in trees
Earthen packing
Termite noises and wood excavation
Piles of termite frass in or around the home
Presence of wings
Sagging floors and hollow wood
Fig 3: Termite infection on plant a) Bauhinia racemosa (Aapta) b) Azadirachta indica (Neem) (Source: Yasmeen et al., 2018)
Subterranean Termite Castes
Fig 4: A and B) primary reproductive C and D) secondary reproductive E) soldier and F) worker (image source: https://cdn.orkin.com) Page | 7
1) Primary Reproductive Mature subterranean colonies, at certain times of the year has produce large number of winged swarmer or “alates” that has eventually become king and queen termites. These royal termites are dark coloured and has with functional eyes. This swarmer loses wings after a short flight where they select a mate. The new king termite remains virtually unchanged after losing his wings. However, as the new queen begins to produce eggs her abdomen grows larger with the development of her ovaries. As she stretches, the segments of her body pull further apart showing the white membranes between segments of her abdomen. This gives queen a striped appearance. The eastern subterranean termite queen has stretch until she is about 14.5mm in length. At this point she is an egg laying machine, producing over 500 offspring a year.
Fig 5: Primary reproductive (image source: www.colonialpest.Com)
2) Secondary Reproductive The termite colony originates from a single pair of reproductive swarmer; the king and queen. However, if the king or queen should die, other individual within colony has starts to develop functional reproductive organs to their place. These individuals are called secondary reproductives. Secondary reproductives are light in colour, larger than worker and never develop wings. In mature colonies a secondary reproductive caste can develop even though there is still a producing queen present. When these are the secondary reproductive caste member has produce majority of the eggs, causing colony to grow at a much faster rate. Although no individual secondary reproductive can produce as many eggs as the queen, several hundred of them may exist in a single colony thus producing thousands of eggs. Secondary reproductives may also develop in satellite nest where a group of workers have become separated from the parent colony. This splitting or budding of the nest expand the original colonies foraging territory.
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3) Worker Caste
Fig 6: Worker termite (image source: https://cdn.orkin.com)
Subterranean termite workers are the caste found in infested wood. The workers are responsible for all of the labour in the colony. They care for the young, repair the nest, worker built foraging tunnels, locate food feed and groom the other caste, and each other. The youngest termite workers perform the domestic task inside the colony like feeding, grooming and caring for the young, while the older, more expendable workers take on the hazardous jobs of foraging and nest building. The termite workers are both male and female but they are functionally sterile. They are milky white in colour and have no wing and eyes. The body of the termite worker is soft, but its mouth part is very hard and adapted for chewing wood. 4) Soldier Caste
Fig 7: Soldier termite (source image: https://cdn.orkin.com)
Subterranean termite soldiers are the defenders of the colony. They protect the colony against marauding ants and foreign termites when Page | 9
foraging tubes or gallery are broken into, the soldier congregate around the break to stand guard against the invaders. Soldiers are similar to the termite workers; they are blind, soft bodied and wingless. However, the soldiers have an enlarged, hard, yellowish brown head which has wings adapted for fighting. The head has a pair of very large mandibles or jaws that are use to puncture, slice and kill enemies (primarily ants). However, the large mandibles prevent the soldier from themselves, so they must rely on the workers for food. Life Cycle Winged primary reproductives are produced in mature colonies. In HonKong, they usually fly for mating (swarm) on warm day after rain in spring. When the winged male and female reproductive’s land on ground, they will shed their wings and pair off to search for suitable herbage to build up a new colony. After mating, the new queen stars laying eggs in about a week. Larvae hatch from the eggs and develops into different caste such as nymphs, worker, soldiers, primary and supplementary reproductive’s during the growth of the colony. The workers are creamy white, soft bodied wingless and blind. Workers, together with nymphs are the most numerous individuals in a termite colony. Since they are responsible for expanding the nest, building tunnels and ingesting food, they are the cuprites’ for causing structural damage. The soldiers also have creamy white and soft bodies but their heads are brownish and elongated with a strong pair of jaws. Soldiers are responsible for protecting the colony from invaders like ants. According to Edward and mill (1986), there are three general developmental stages; egg, immature, adults in termites life cycle known as “incomplete metamorphosis”. The role of the winged adult is dispersal and reproduction, the actual work of the colony and expansion of the colonies foraging is done by the cast of workers, while the soldiers defend the colony (Forschler and Jenkins 2000) winged adults (allates or swarmer) represent a primary cast of individuals within the termite colony. They disperse from their colony of origin in a series of flights or swarmers at precise time of the year. Adults are attracted to lights, where pairing begins. The swarmer on reaching the ground shed their wings and started searching for a suitable place to initiate colony. The males are attracted to the female by the scent or pheromone. They dig into the wood or moist soil depending on the species and form a chamber. Mating occurs within the nuptial chamber and the queen once fertilized; initiate the new colony as she begins to lay eggs.
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Fig 8: Life cycle of termite (image source: science.Howstuff-works.com)
Termite Behaviour 1) Nutrition of Termites Termite mainly feed on wood and wood products containing cellulose like paper, mulch, cardboard and fabrics made of plant material. Basically, worker termites are travels away from the nest to search for food and building tunnels while they are foraging. Once food source is found, mere termites will be sent to feed on the food. Termites have microorganism in their intestine to help digesting the cellulose. They serve an important ecological role in the decomposition of cellulose material that cannot be present of the enzyme, cellulase (Pearce 1997). According to (Abe et al, 2000), primitive do not produce sufficient cellulose for survival, but contain protozoan in their gut that aid in cellulase breakdown. This interaction is an obligate mutualism for both termite and protozoan (Abe et al, 2000). Higher termites (Termitidae) do produce sufficient cellulase in their mid-gut to digest adequate nutrition from cellulose, still form mutualism with bacteria and fungi biota (Abe et al, 2000). Under natural conditions in the desert, termites feed on dead plant materials, including roots, leaf litters, grass, caltu, skeletons, dung and humus (Jones and Nutting, 1989). According to Page | 11
Su and Scheffrahn (1990), although the feeding activity of termites is critical to the recycling of nutrients in the ecosystem, unfortunately they infest human made structures and damage lumber, sheetrock, wallpaper, wood panel and furniture’s. Termites spend their entire life in soil or within their source of food, and once removed from their protected environment and favorable humidity, they die (Edward and Mill, 1986). According to Lee (2002), termites do feed on concrete, stucco, fibreglass insulation or other non-organic material. However, they can damage these materials and use them to line and support tubes. Nutrition and Digestion in Higher Termites Diets and their digestion, differ among lower and higher termites. Termitidae ingest a wide range of materials. e.g.: Leaves, roots, grass, dung and soil (humus) cultivating species (Wood and Johnson 1989) There are two groups within the Termitidae. 1) Fungus-Cultivating Termites of fungus cultivating subfamily macrotermitinae create large fungal gardens in their nests. These gardens are constructed by a assembling partially digested plant material that is permeated and further digested by fungal mycelium (Wood and Johnson, 1989) viz. plant polysaccharide and lignin partially digested within comb (Rohrmannand Rossmann, 1980; Veivers.et.al 1991).The garden fungi mostly belong to genus Termitomyces and exclusively found in termite nests. They are maintained and distributed by termites. Enzymes for hemicellulose digestion i.e. xylanases, may also be supplied by fungus (Rouland et. al, 1988). In any case, the nature and relative importance of ingested fungal enzymes varies from species to species. 2) Non-Fungus Non fungus cultivating higher probably digest their food, including cellulose, by enzyme that are produced by their own mid gut and salivary glands (Slaytor, 1992). Cellulytic activity and growth rate on cellulose was very low and insignificant (Breznakand Brune, 1994). Cellulolytic genera are cellulomonas and bacillus (Konigand Breuning, 1997). Nutrition and Digestion in Lower Termites Many species of lower termites feed almost exclusively on wood, although this food is hard to digest and poor in nutrients, particularly Page | 12
nitrogen. Therefore many termites prefer wood that has been attacked by fungi, which is easier to utilize and richer in protein due to the presence of fungal mycelia. Termite and Fungus Association There is a large diversity of fungi associated with termites and their presence with these insects has often been classified as beneficial because these symbiotic associations provide termite’s metabolic pathways for processing carbon and nitrogen fixation from the breakdown of lignocellulosic components (Sands 1969, Lima and Costa Leonardo 2007). The fungus viz. Alternaria sp., Penicillium sp., Mucor sp., Rhizopus sp., Aspergillus sp., Cladosporium sp., Fusarium sp., Gliomastix sp., Trichoderma sp., Actinomycetes sp., Basidiomycetes sp. and Hypomycetes sp. are symbiotic association with different genera of termites. 3) Communication Termites in same colony communicate with each other in several means. Basically they communicate by a chemical called “pheromone” which odour is different in each colony. e.g. worker termites will lay a pheromone trail to guide others to a food source. Sound produced by worker and soldier termites by banging their heads on mud tube surface is also a communication used to alert other members. Mutual exchange of nutrients and transfer of food between castes is another means of communication. Conclusion In present study make report on termite and their thorough classification based on habitat viz. dry wood, damp wood and subterranean and their infection to plant. The termite biology, brief explanation about life cycle, communication and nutrition of termite and their nutrition interrelated to types of termites viz. lower and higher. The termite and fungus has symbiotic association. Fungus viz. Alternaria sp., Penicillium sp., Mucor sp., Rhizopus sp., Aspergillus sp., Cladosporium sp., Fusarium sp., Gliomastix sp., Trichoderma sp., Actinomycetes sp., Basidiomycetes sp. and Hypomycetes sp. are symbiotic association with different genera of termites. References 1.
Sands WA. The association of termites and fungi. In: Krishna K, Weesner FM, editor. Biology of termites. New York, Academic Press, 1969, 495-519.
2.
Grimaldi D, Engel MS. Evolution of the Insects. Cambridge University Press, 2005, 145. Page | 13
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Engel MS, Krishna K. Family-group names for Termites (Isoptera). American Museum Novitates 3432, 2004, 1-9.
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Paul BB, Rueben JM. Arizona Termites of Economic importance. University of Arizona Press, Tucson, AZ, 2005, 9-17.
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Harris WV. Termites: Their Recognition and Control. Tropical Agric. Series, 1961, 53-64.
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Abe T, Bignell DE, Higashi M. Termites: Evolution, Socially, Symbioses, Ecology. Kluwer Academic Publishers, 2000, 256.
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https://cdn.orkin.com
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Light SF. The Damp- Wood Termite, Paraneotermites simplicicornis. In: Termites and Termite Control. University of California Press, Berkeley, C.A, 1994, 311-313.
9.
Noirot C. The nests of termites. In Biology of Termites (Ed. By K. Krishna and F.M. Weesner). New York and London (Academic Press), 1970, 2:73-125.
10. Su NY, Scheffrahn RH. Termites Aspects of Buildings. In: Abe T, Bignell DE, Higsahi M. eds. Termites: Evolution, Sociality, Symbiosis and Ecology. Kluwer Academic Publishers. Dordrecht, the Netherlands, 2000, 437-453. 11. www.colonialpest.Com 12. Edwards R, Mill AE. Termites in Buildings. Their Biology and Control. Rentokil Ltd, West Sussex UK, 1986, 54-67. 13. Forschler BT, Jenkins TM. Subterranean Termites in the Urban Landscape: Understanding their social structure is the key to successfully implementing population management using bait technology. Urban Ecosystems. 2000; 4:231-251. 14. Pearce MJ. Termites Biology International, New York, 1997.
and
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15. science.Howstuff-works.com 16. Jones SC, Nutting WL. Foraging Ecology of Subterranean Termites in the Sonoran Desert. In: Special Biotic Relationships in the Arid Southwest. University of New Mexico Press, Albuquerque NM, 1989, 79-106. 17. Su NY, Scheffrahn RH. Economically important Termites in the United State and their Control. Socio-biology. 1990; 17:77-94. Page | 14
18. Lee CY. Subterranean Termite Pest and their Control in the Urban Environment in Malaysia. Socio-biology. 2002; 40:3-9. 19. Wood TG, Johnson R. The mutualistic association Macrotermitinae and Termitomcyes, 1989, 69-92.
between
20. Rohrmannnd GE, Rossmann AY. Nutrient strategies of Macrotermes ukuzii (Isoptera: termitidae). Pedobiologia. 1980; 20:61-73. 21. Rouland C, Lenoir F, Le Page M. The role of the symbiotic fungus in the digestive metabolism of several species of fungus growing termites. Comp. Bio-chem. Physiol. 1991; 99A:657-663. 22. Slayter M. Cellulose digestion in termites and cockroaches: What role do symbionts play? Comp. Bio-chem. Physiol. 1992; 103B:775-784. 23. Koing H, Breuning A. Okosystem Termitendram Spekt. Wissenschaft. 1997; 4:68-76. 24. Juliana Toledo Lima, Ana Maria Costa-Leonardo. Food resources exploited by termites (Insecta: Isoptera), Biota Neo trop. 2007; 7(2):243-250. 25. Yasmeen Shaikh, Gulfisha Shaikh, Shivaji Chavan. Diversity of subterranean termites and their associated fungi on infected four plant species in Swami Ramanand Teerth Marathwada University Campus Nanded, International Journal of Entomology Research. 2018; 3(1):4951.
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Chapter - 2 Entomopathogenic Nematode a Potential Tool for Biological Control of Insect Pests
Authors Saroj Yadav Department of Nematology, College of Agriculture, CCS HAU, Hisar, Haryana, India Jaydeep Patil Department of Nematology, College of Agriculture, CCS HAU, Hisar, Haryana, India
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Chapter - 2 Entomopathogenic Nematode a Potential Tool for Biological Control of Insect Pests Saroj Yadav and Jaydeep Patil
Entomopathogenic nematodes (EPNs) belonging to the families Steinernematidae and Heterorhabditidae (Rhabditida) have been used as effective biological control agents against a wide spectrum of insect pests. Steinernematids are symbiotically associated with entomopathogenic bacteria (EPBs) from the genus Xenorhabdus, and heterorhabditid nematodes are symbiotically associated with EPBs from the genus Photorhabdus. The bacterial symbionts produce wide range of toxins, hydrolytic exoenzymes, and antibacterial compounds. These compounds not only kill and bioconvert infected larvae, but also preserve the cadavers from being consumed by other soil organisms. There have been recent advances in the technology of mass producing and formulating nematodes. These recent advances, together with the need to reduce pesticide use, have resulted in a surge of scientific and commercial interest in EPNs and their symbiotic bacteria. Many species and strains of potential control organisms have to be evaluated to elaborate a new biological control technique. Keywords: Biological control agents, entomopathogenic nematodes, mass production and formulations etc. Introduction Nematodes are non-segmented, elongated roundworms that are colorless, without appendages, and usually microscopic. There are nonbeneficial and beneficial nematodes. Non-beneficial nematodes cause damage to crops and other types of plants are also called “plant parasitic nematodes”. Beneficial nematodes attack soil-borne insect pests, yet are not harmful to humans, animals, plants, or earthworms, and can therefore be used as biological control organisms (Denno et al., 2008). Beneficial nematodes cause disease in insect are referred to as “entomopathogenic” and have the ability to kill insects. Indiscriminate use of chemical pesticides for the management of insect Page | 19
pests in different agro ecosystems has been raised many environmental concerns viz. ground water contamination, residue in food, resistance development, soil pollution, air pollution, secondary pest outbreak, pest resurgence, etc. (Zimmerman and Cranshaw 1990). As a substitute to pesticides, biological control agents like entomopathogenic fungi, bacteria, viruses and nematodes have gained more importance due to its ecofriendly properties. Biopesticides have been accepted as important component of Integrated Pest Management. Selected species of fungi, bacteria, viruses and nematodes with established insecticidal activities constitute biocontrol agents which have been formulated into biopesticides for the management of insect pests. So far, 3,000 microbial species have been identified to cause diseases in insects (Dhaliwal et al. 2013). Entomopathogenic nematodes (EPNs) in the genera Steinernema and Heterorhabditis are obligate parasites of insects (Poinar, 1990; Lewis and Clarke, 2012). Nematodes have a symbiotic relationship with a bacterium (Xenorhabdus spp. are associated with steinernematids and Photorhabdus spp. are associated with heterorhabditids) (Poinar, 1990). Infective juveniles nematodes (IJs), the only free-living stage, enter hosts through natural openings, or in some cases, through the cuticle. After entering the host’s hemocoel, nematodes release their symbiotic bacteria and the nematodes molt and complete up to three generations within the host, after which IJs exit the cadaver to search out new hosts (Kaya and Gaugler, 1993). Entomopathogenic nematodes are effective at controlling a variety of economically important pests. Entomopathogenic nematodes are currently produced by different methods either in vivo or in vitro (solid and liquid culture) (Friedman, 1990). The keys to success with entomopathogenic nematodes are (1) understanding their life cycles and functions; (2) matching the correct nematode species with the pest species; (3) applying them during appropriate environmental conditions (soil temperature, soil moisture, sunlight); and (5) applying them only with compatible pesticides. Because entomopathogenic nematodes are living organisms, they require careful handling to survive shipment and storage as well as appropriate environmental conditions to survive in the soil after application. Entomopathogenic Nematodes Biology The parasitic cycle of nematodes is initiated by the third stage infective juveniles. These non-feeding juveniles locate and invade suitable host insects through natural body openings (i.e. anus, mouth, and spiracles) or even
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through the cuticle when the genus Heterorhabditis is concerned. Once inside the host, infective juveniles invade the hemocoel and release a symbiotic bacterium, which is held in the nematode’s intestine (Poinar 1990). The bacteria cause a septicemia, killing the host within 24-48h. The infective juveniles feed on the rapidly multiplying bacteria and disintegrated host tissues. About 2-3 generations of the nematode are completed within the host cadaver. When food reserves are depleted, nematode reproduction ceases and the offspring develop into resistant infective juveniles which disperse from the dead host, and are able to survive in the environment and to seek out new hosts. Host Range The nematode-bacterium complex kills insects so rapidly that the nematodes do not form the intimate, highly adapted, host-parasite relationship characteristic of other insect nematode associations, e.g., mermithids. This rapid mortality permits the nematodes to exploit a range of hosts that spans nearly all insect orders, a spectrum of activity well beyond that of any other microbial control agent. In laboratory tests, S. carpocapsae alone infected more than 250 species of insects from over 75 families in 11 orders (Poinar 1975). The nematodes attack a far wider spectrum of insects in the laboratory where host contact is assured, environmental conditions are optimal, and no ecological or behavioral barriers to infection exist (Kaya & Gaugler 1993, Gaugler et al. 1997). For example, foliage feeding lepidopteran larvae are highly susceptible to infection in Petri dishes, but are seldom impacted in the field, where nematodes tend to be quickly inactivated by the environmental extremes (i.e., desiccation, UV radiation, temperature) characteristic of exposed foliage. Behavioral barriers also restrict nematode efficacy to a few selected hosts or host groups (Gaugler et al. 1997). Selection of Entomopathogenic Nematodes Selection of an EPN for control of a particular pest insect is based on several factors that include the nematode’s host range, host finding or foraging strategy, tolerance of environmental factors and their effects on survival and efficacy (temperature, moisture, soil type, exposure to ultraviolet light, salinity and organic content of soil, means of application, agrochemicals, and others). The four most critical factors are moisture, temperature, pathogenicity for the targeted insect, and foraging strategy (Kaya and Gaugler, 1993). Compatibility with Other Agents and Agrochemicals The combination of EPNs and other control agents has proved to be Page | 21
synergistic and produces higher mortality than either agent alone. For example, Koppenhofer and Kaya (1997) showed additive and synergistic interaction between EPNs and Bacillus thuringiensis for scarab grub control. Entomopathogenic nematodes are often applied to sites and ecosystems that routinely receive other inputs that may interact with nematodes including chemical pesticides, surfactants (e.g., wetting agents), fertilizers, and soil amendments. Often it is desirable to tank mix one or more inputs to save time and money. Infective juveniles are tolerant of short exposures (26h) to most agrochemicals including herbicides, fungicides, acaricides, and insecticides (Rovesti and Deseo, 1990; Ishibashi 1993), and therefore, can often be tank-mixed. However, some pesticides can reduce nematode infectivity and survival (Grewal et al. 1998). Due to the continuous introduction of new active ingredients and formulations in different market segments and to differences in susceptibility of nematode species to pesticide formulations, it is difficult to provide up-to-date information. However, heterorhabditids tend to be more sensitive to physical challenges, including pesticides, than steinernematids. Host Finding Mechanism of Entomopathogenic Nematodes Host-finding strategies of entomopathogenic nematode will help you properly match nematode species to pest insects to ensure infection and control (Gaugler 1999). Only infective juvenile stage of entomopathogenic nematodes will survive in the soil and find and penetrate insect pests. Infective juvenile locate their hosts in soil by means of two strategiesambushing and cruising (Gaugler et al. 1989). Ambusher species include Steinernema carpocapsae and S. scapterisici; cruisers include Heterorhabditis bacteriophora and S. glaseri. S. riobrave and S. feltiae do a bit of both ambushing and cruising (Campbell and Gaugler 1997). Ambushing: Entomopathogenic nematodes that use the ambushing strategy tend to remain stationary at or near the soil surface and locate host insects by direct contact (Campbell et al. 1996). An ambusher searches by standing on its tail so that most of its body is in the air, referred to as “nictation”. The nictating nematode attaches to and attacks passing insect hosts. Ambusher entomopathogenic nematodes most effectively control insect pests that are highly mobile at the soil surface, such as cutworms, armyworms, and mole crickets. Cruising: Entomopathogenic nematodes that use the cruising strategy are highly mobile and able to move throughout the soil profile. Cruisers locate their host by sensing carbon dioxide or other volatiles released by the Page | 22
host. Cruiser entomopathogenic nematodes are most effective against sedentary and slow-moving insect pests at various soil depths, such as white grubs and root weevils. Mass Production Entomopathogenic nematodes can be mass-produced by in-vivo or invitro methods. The wax moth, G. mellonella larvae are most commonly used to rear nematodes because of their commercial availability. Using the in-vivo process, yields between 0.5x105-4x105 infective juveniles per larva, depending on the nematode species, have been obtained. During the past few years a distinct cottage industry has emerged, which utilizes the in-vivo process for nematode mass production for sale, especially in the home lawn and garden markets. The in-vivo process, however, lacks any economy of scale; the labor, equipment, and material (insect) costs increase as a linear function of production capacity. Perhaps even more important is the lack of improved quality while increasing scale. The in-vivo nematode production is increasingly sensitive to biological variations and catastrophes as scale increases (Friedman 1990). First time developed the artificial culture (in-vitro) methods for entomopathogenic nematodes for S. glaseri (Glaser, 1932). The first successful commercial scale monoxenic culture was developed by Bedding and has come to be known as “solid” culture (Bedding 1981). In this method, nematodes are cultured on a crumbed polyether polyurethane sponge impregnated with emulsified beef-fat and pig’s kidneys along with symbiotic bacteria. Using this method approximately 6x105 - 10x105 infective juveniles/g of medium were achieved (Bedding 1984). Friedman also reported the development of a liquid fermentation technique for large-scale production of nematodes (Friedman 1990). In this method, costs of production decrease rapidly up to a capacity of approximately 50x1012 infective juveniles/month. This method allows consistent production of steinernematids in as large as 80,000 litter fermenters. Recent improvements in the nematode fermentation and media formulation processes have resulted in further improvements in nematode quality and yields Application Technology Technology must also be developed which insure the successful application of the entomopathogenic nematode (EPN’s) to the target site and also target insect, thereby increasing the probability of entomopathogenic nematode-insect interaction. Insect life-stage susceptibility is critical, since different life stages of different species are not equally susceptible. Many Page | 23
times, larval stages of insects such as different borers are not accessible to entomopathogenic nematodes. Evaluating the most appropriate entomopathogenic nematode strain is important for efficacy and commercial development. Nematodes’ ability to effectively kill the target pest have been influenced by either abiotic factors such as soil type, soil temperature and moisture, or biotic factors, including pathogens and predators, can greatly influence the. Application techniques, including field dosage, volume, irrigation and appropriate application methods are very important, especially if nematodes are to be integrated with other control strategies. Compatibility with a wide range of pesticides has been demonstrated. This has benefited the successful introduction with existing Integrated Pest Management programs. Crop morphology and phenology must be considered in predicting whether nematodes are viable control candidates. Table: Efficacy of entomopathogenic nematodes against different insect pests Crop
Apple
Cabbage
Citrus
Coffee
Pest
EPN species
Dosage (IJs)
Mortality Reference (s) (%)
Cydia pomonella (Linnaeus)
Steinernema carpocapsae
5×109/ha
83
Lacey and Unruh (1998)
Hoplocampa 1×105/500 testudinca S. carpocapsae cm long Klug branch
100
Belair et al (1998)
Plutella xylostella (Linnaeus)
S. carpocapsae
75/cm2
80
Schroer and Ehlers (2005)
Diaprepes abbreviatus (Linnaeus)
S. riobrave
Soil baiting technique
65-80
Stuart et al (2004)
Hypothenemus Heterorhabditis hampei spp. S. (Ferrari) carpocapsae
-
-
Field and plantation crops
Maladera insanabilis Brenske
H. bacteriophora, S. feltiae,S. glaseri
Tomato
Spodoptera litura
Steinernema carpocapsae
Allard and Moore (1989), High Castillo and mortality MarbanMendoza (1996) Significant Bhatnagar et reduction al. (2004)
77.5 and 20000 Saroj Yadav et 75 per cent IJs/Plant. al (2016) mortality
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Mushroom
Polyphagous pest
Potato Stored product Turf field
Lycoriella auripila (Winnertz)
S. feltiae
3×106 /tray
91-93
Grewal et al. (1993)
Helicoverpa armigera (Hubner)
Local isolate EPN-3 and EPN -16 (Gujarat)
2000/5 chickpea plant /pot
96.8 and 70.9
Vyas (2003), Vyas et al (2002)
H. indica
90/larva
97.5
Holotrichia consanguinea (Blanchard)
H. indicus
-
Spodoptera litura Fabricius
H. indica, S. glaseri
Agrotis ipsilon Neoaplectana (Hufnagel) sp.
Significant reduction
Singh et al. (2001)
-
-
Saravanapriya and Subramanian (2007)
-
100
Singh (1977)
100
RamosRodriguez et al. (2006)
44-66
Selvan et al. (1993)
Plodia S. riobrave, S. 50/ interpunctella carpocapsae, S. individual (Hubner) feltiae Popillia japonica Newman
S. glaseri
Prabhuraj et al. (2006)
5×109/ha
Entomopathogenic Nematodes Formulation Generally, the components of the formulations are: an active ingredient, a carrier and additives. Active ingredients in the formulations are EPNs, whereas the carriers used are solids, liquids, gels, and cadavers. The additives are various substances with different functions, such as absorbents, adsorbents, emulsifiers, surfactants, thickeners, humectants, dispersants, antimicrobials, and UV-ray protectors (Grewal, 2002). The main purpose of the additives used in the formulations has been to increase the survival and maintain the virulence of the EPNs. Formulations for Storage and Transport Aqueous Suspension: The most common EPN formulation is an aqueous suspension. It has been used mainly for storage, transportation, and application (Chen & Glazer, 2005). Storage temperatures between 4 and 15°C have produced survival times of 6–12 months for Steinernema spp. and 3–6 months for Heterorhabditis spp. (Hazir et al., 2003). However, there are many factors that affect their survival time: sedimentation, high oxygen demand, decreased response of some species at low temperatures,
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susceptibility to microbial contamination, special storage conditions and appropriate concentration for each species (Grewal & Peters, 2005). Synthetic Sponges: The formulation in polyurethane sponges is accomplished by applying an aqueous suspension of 500–1000 IJs cm2, which results in an amount of 5–25 million IJs per sponge, which is subsequently placed in a plastic bag for storage. The EPNs formulated in sponges achieve a survival time of 1–3 months at 5–10°C (Grewal, 2002) and for their release, the sponges are dipped in a bowl with water. Gels: Yukawa and Pitt (1985) described a system for nematode storage and transport. The EPNs were homogeneously mixed with absorbent materials, such as activated carbon powder, to form a cream, but this formulation has presented the drawbacks of high cost, unpleasant handling and low stability at room temperature (Grewal, 1998). Clay and Powder: Bedding (1988) encapsulated S. feltiae, Steinernema bibionis, Steinernema glaseri, and Heterorhabditis heliothidis in a hygroscopic attapulgite clay formulation with survival time of 8 weeks at 23°C. The formulation was called a “sand wich” type, because the EPNs are stored between two layers of clay. Products with this formulation were sold, but soon were discontinued due to poor storage stability, clogging of the spray nozzles, and a low nematode-clay proportion (Grewal, 2002). Formulations for Direct Application in the Field Gel: With the aim of eliminating the disadvantages of releasing the EPNs from the alginate granules with sodium citrate, Kaya and Nelsen (1985) encapsulated the EPNs S. feltiae and H. heliothidis in calcium alginate granules coated by lipid membranes and fed to larvae of Spodoptera exigua Hübner. While feeding on the capsules, the larvae released the EPNs. When moisture was present, larval mortality was nearly 100%. Infected Cadavers: The cadavers are another way to apply EPNs in the field (Raja et al., 2015). In this formulation, the insect cadaver serves as a reservoir to store the EPNs and then they are applied in the field. Laboratory tests have indicated that this method of application produces a better distribution of the EPNs in the soil than that obtained with the aqueous solution (Shapiro & Glazer, 1996), increases infectivity (Shapiro & Lewis, 1999) and is more effective (Shapiro-Ilan et al., 2003).
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Table: Commercially available Entomopathogenic Nematodes Product Name
Nematode Species
Target Pests
Producer
Ecomask
Steinernema carpocapsae
Caterpillars
Bio Logic
Savior Weevil larvae
Steinernema carpocapsae
Caterpillars
Thermo-Trilogy
Guardian
Steinernema carpocapsae
Caterpillars
Hydro Gardens
J-3 Max
Steinernema carpocapsae, Heterorhabditis bacteriophora
Caterpillars
The Green Spot Bio Logic
Heteromask
Heterorhabditis bacteriophora
Weevils, grubs
Lawn Patrol
Heterorhabditis bacteriophora
Weevils, grubs Hydro Gardens
Scanmask
Steinernema feltiae
Fungus Gnats
Bio Logic
Entonem
Steinernema feltiae
Fungus gnats
Koppert
Nemasys
Steinernema feltiae
Fungus gnats
E.C. Geiger
Factors Affecting Market Expansion of Entomopathogenic Nematodes
Markets, Crops and Target Insects: Efficacy of entomopathogenic nematodes under the field is limited. Different product labels listed are unsuitable to the target insects and they are effect against the few selected insects and environment. Efficacy against certain insects is significantly lower than competitive products. Certain product labels recommend suboptimum application rates. Limited data on cost effectiveness in IPM programs.
Formulation and Shelf Life: Refrigeration requirements and limited room temperature shelf life. Certain formulations require time for mixing and preparing spray solution. Sub-optimum storage by the distributors, dealers and growers.
Usage Directions: Different product labels lack proper application directions and application requirements such as temperature, moisture, irrigation and timing. Product coverage is impractical in certain applications. Improper handling, mixing and application by end users.
Technical Support: Limited experience and knowledge of farm advisors and extension personnel.
Cost and Gross Margins: In general, products are more expensive than competitive products. Gross margins are generally lower for the distributors than competitive products.
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Advantages of Entomopathogenic Nematode
Broad host range of insect pest
Rapid kill of insects
Can actively seek or ambush host
In vivo and in vitro mass production capability
Application through conventional equipment
Safety: for all vertebrates, most non-target invertebrates, and the food supply
Little or no registration required
Disadvantages
High cost of production
Limited shelf-life and refrigerated storage required
Environmental limitations: requirements for adequate moisture (to enable survival and infectivity) and temperatures (above or below that required for optimal infectivity), sensitivity to UV radiation, lethal effect of several pesticides (nematicides, fumigants and others), lethal or restrictive soil chemistries (high salinity, high or low pH, etc.).
Conclusion and Future Prospects Entomopathogenic nematodes gain higher popularity in controlling insect pest due to the safety environmental concern. To overcome limitations in their use current efforts for improving mass-production techniques and lowering the manufacturing costs and in developing more advanced carriers and techniques in formulation to widen the IJs shelf-life. Moreover, genetic improvement may be considered as a novel venue that would help increasing nematode performance and efficacies in the field. Further advancements are needed in the symbiotic bacteria Photorhabdus and Xenorhabdus are highly insecticidal against certain groups of insect pests, the potential of insecticidal toxins isolated from these bacteria as novel insecticidal proteins for insect control. Overall, the future use of EPNs is promising, given all the advantages they possess, as well as the increasing demand for any virulent microbial pathogen to help mitigate the environment and resistance pressure of synthetic chemical insecticides. References 1.
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Technol, 1990, 153-172. 14. Gaugler R, Lewis E, Stuart RJ. Ecology in the service of biological control: the case of entomopathogenic nematodes. Oecologia. 1997, 109:483-489. 15. Gaugler R. Matching Nematode and Insect to Achieve Optimal Field Performance. In Workshop Proceedings: Optimal Use of Insecticidal Nematodes in Pest Management, Edited by S. Polavarapu, Rutgers University, 1999, 9-14. 16. Gaugler RJ, Campbell McGuire T. Selection for Host Finding in Steinernema feltiae. Journal of Invertebrate Pathology. 1989; 54:363372. 17. Glaser RW. Studies on Neoplectana glaseri, a nematode parasite of the Japanese beetle (Popillia japonica). New Jersey Department of Agriculture Circular No. 211, 1932. 18. Grewal PS, Tomolak M, Kiel CBO, Gaugler R. Evaluation of genetically selected strain of Steinernema feltiae against the mushroom sciarid fly Lycoriella mali. Ann Appl Biol. 1993; 123:695-702. 19. Grewal PS, Peters A. Formulation and quality. In: Grewal PS, Ehlers RU, Shapiro-Ilan DI. (eds): Nematodes as Biocontrol Agents. Ox ford shire, CABI, 2005, 79-90. 20. Grewal PS, Webber T, Batterley DA. Compatibility of Steinernem feltiae with chemicals used in mushroom production. Mushroom News. 1998; 46:6-10. 21. Grewal PS. Formulation and application technology. In: Entomopathogenic Nematology, Gaugler R. Ed., Wallingford, UK: CABI Publishing, 2002, 265-288. 22. Grewal PS. Formulations of entomopathogenic nematodes for storage and application. Japanese Journal of Nematology. 1998; 28:68-74. 23. Hazir S, Kaya HK, Stock SP, Keskin N. Entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) for biological control of soil pests. Turkish Journal of Biology. 2003; 27:181-202. 24. Ishibashi N. Integrated control of insect pests by Steinernema carpocapsae, In R.A. Bedding, R. Akhurst &. K. Kaya (eds.), Nematodes and Biological Control of Insects. East Melbourne, CSIRO. 1993; 234:105-113.
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25. Kaya HK, Gaugler R. Entomopathogenic nematodes. Annu. Rev. Entomol. 1993; 38:181-206. 26. Kaya HK, Nelsen CE. Encapsulation of Steinernematid and Heterorhabditid nematodes with calcium alginate: a new approach for insect control and other applications. Environmental Entomology. 1985; 14:572-574. 27. Kaya HK. Soil ecology. In: Gaugler, R, Kaya, HK (Eds.), Entomopathogenic Nematodes in Biological Control. CRC Press, Boca Raton, FL, 1990, 93-116. 28. Koppenhofer AM, Kaya HK. Additive and synergistic interaction between entomopathogenic nematodes and Bacillus thuringiensis for scarab grub control. Biol. Control. 1997; 8:131-137. 29. Lacey LA, Unruh TR. Entomopathogenic nemtodes for control of codling moth, Cydia pomonella: effect of nematode species, concentration, temperature, and humidity. Biol Control. 1998; 13:1-8. 30. Lewis EE, Clarke DJ. Nematode parasites and entomopathogens. In: Vega FE, Kaya HK. (Eds.), Insect Pathology, 2nd Edition. Elsevier, Amsterdam, 2012, 395-424. 31. Poinar Jr GO. Entomogenous nematodes, a manual and host list of insect-nematode associations. Leiden EJ. Brill, 1975, 254. 32. Poinar JR GO. Biology and taxonomy of steinernematidae and heterorhabditidae. In: Gaugler R, Kaya HK. (Eds.), Entomopathogenic Nematodes in Biological Control. CRC Press, Boca Raton, FL. 1990, 23-62. 33. Prabhakar M, Prasad YG, Venkateswarlu B. New record of Hexamermis dactylocercus Poinar Jr. and Linares (Nematoda: Mermithidae) parasitizing red hairy caterpillar, Amsacta albistriga (Walker) (Lepidoptera: Arctiidae) from India. J Biol Control. 2010; 24(3):285-87. 34. Raja RK, Hazir C, Gümüs A, Asan C, Karagöoz M, Hazir S. Efficacy of the entomopathogenic nematode Heterorhabditis bacteriophora using different application methods in the presence or absence of a natural enemy. Turkish Journal of Agriculture and Forestry. 2015; 39:277-285. 35. Ramos-Rodriguez O, Campbell JF, Ramaswamy SB. Pathogenicity of three species of entomopathogenic nematodes to some major storedproduct insect pests. J Stored Prod Res. 2006; 42:241-52. 36. Rovesti L, Deseo KV. Compatibility of chemical pesticides with the Page | 31
entomopathogenic nematodes, Steinernema carpocapsae Weiser and S. feltiae Filipzev (Nematoda: Steinernematidae). Nematologica. 1990; 36:237-245. 37. Saravanapriya B, Subramanian, S. Pathogenicity of EPN to certain foliar insect pests. A Pl Prot Sci. 2007; 15(1):219-22. 38. Schroer S, Ehlers RU. Foliar application of the entomopathogenic nematode Steinernema carpocapsae for biological control of diamondback moth larvae (Plutella xylostella). Biol Control. 2005; 3:81-6. 39. Selvan S, Gaugler R, Campbell JF. Efficacy of entmopathogenic nematode strains against Popillia japonica (Coleoptera: Scarabaeidae) larvae. J Econ Ent. 1993; 86:353-59. 40. Shapiro DI, Glazer I. Comparison of entomopathogenic nematode dispersal from infected hosts versus aqueous suspension. Environmental Entomology. 1996; 25:1455-1461. 41. Shapiro DI, Lewis EE. Comparison of entomopathogenic nematode infectivity from infected hosts versus aqueous suspension. Environmental Entomology. 1999; 28:907-911. 42. Shapiro-Ilan DI, Bruck DJ, Lacey LA. Principles of epizootiology and microbial control. In: Vega FE, Kaya HK. (Eds.), Insect Pathology, 2nd Edition. Elsevier, Amsterdam, 2012, 29-72. 43. Shapiro-Ilan DI, Lewis EE, Tedders WL. Superior efficacy observed in entomopathogenic nematodes applied in infected-host cadavers compared with application in aqueous suspension. Journal of Invertebrate Pathology. 2003; 83:270-272. 44. Singh V, Yadava CPS, Bhardwaj SC. Potential use of entomopathogenic nematodes in the management of white grub. Indian J Ent. 2001; 63(4):467-70. 45. Stuart RJ, Shapiro-Ilan DI, James RR, Nguyen KB, McCoy CW. Virulence of new and mixed strains of the entomopathogenic nematode Steinernema riobrave to larvae of the citrus root weevil Diaprepes abbreviatus. Biol Control. 2004; 30:439-45. 46. Vyas RV, Patel NB, Patel P, Patel DJ. Efficacy of entomopathogenic nematodes against Helicoverpa armigera on pigeonpea. Int Chickpea Pigeonpea News. 2002; 9:43-44. 47. Vyas RV. Entomopathgenic nematodes-a new tool for management of Page | 32
insect pests of crops. In: Hussaini SS, Rabindra RJ, Nagesh M (eds) Current Status of Research on Entomopathogenic Nematodes in India. PDBC, Bangalore, India, 2003, 113-19. 48. Yadav S, Siddiqui AU, Patil J. Comparative efficacy of different populations of Steinernema carpocapsae against Spodoptera litura on tomato. The Escoscan. 2016; 9:13-18 49. Yukawa, T, Pitt, JM. Nematode storage and transport. WIPO Patent No. WO 85/03412, 1985. 50. Zimmerman RJ, Cranshaw WS. Compatibility of three entomogenous nematodes in aqueous solutions of pesticides used in turfgrass maintainance. J Econ Ent. 1990; 83:97-100.
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Chapter - 3 Biological Control of Insects by Birds
Authors Nagamandla Ramya Sri Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India Nagulapally Sneha latha Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India Gautam Kunal Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India Pavan Thakoor Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India
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Chapter - 3 Biological Control of Insects by Birds Nagamandla Ramya Sri, Nagulapally Sneha Latha, Gautam Kunal and Pavan Thakoor
Introduction In the area of integrated pest management, of late, birds are also being considered as an important component. The insectivorous nature of the several important bird species is being exploited for minimizing the insect populations at field level. A good number of bird species are found not only as insect predators but also for their role in complementing the vigour & efficiency of the other biological control agents that are being employed in the bio-suppression of the crop pests. Dissemination of NPV virus through bird droppings fits as a best example to explain such situation. Effective conservation of these insectivorous birds in agricultural ecosystem has a certain yielding on the effective implementation of IPM. AINP has paid a special attention in this regard, and use of these beneficial birds in IPM programmes. Artificial bird nests are also provided to increase the activity of beneficial bird population in and around the agricultural crop fields. Following are the some achievements in this direction. The most common insectivorous species in the agro ecosystem are Cattle Egret, Black Drongo, Indian Myna, Bank Myna, Brahminy Myna, Pied Myna, Rosy Pastor, Starling, House Crow, Jungle Crow, Wagtails, Common Swallow, and House Sparrow and Green Bee-eater1. Nocturnal Barn Owl is an exclusive predator of rodents whereas; the Spotted Owlet largely feeds on the adults of coleopteran and lepidopteran insects. Several experiments were designed to quantify the positive role of the birds in controlling insect pests. Contents Experiments on role of insectivorous birds in agricultural eco-system in different agro- ecological regions on various crops revealed that a total of 48 spp of birds involved in controlling major insect pests belonging to Orthoptera, Coleoptera and Lepidoptera.
At least fourteen species of birds were identified feeding on H. armigera in chickpea in Gujarat, amongst which Rosy Pastor Page | 37
(15.9%), Cattle Egret (3.9%), Indian Myna (37.5%), Bank Myna (34.5%) and Black Drongo (4.9%) were important. The birds alone brought about 73% control of the larval population and thus improved the yield. The grain yield was 218 g/m' in experimental plot as against 120 g/m? In the control plot, where no birds were allowed to feed.
Prey searching efficiency of insectivorous birds was much better when the chickpea variety ICCC-4 was grown at 60 em inter-row distance as compared to 45 em inter-row distance without affecting the yield.
Fixing the perches @ 50/ha in chickpea improved the efficiency of predatory birds like Drongo, Mynas, Sparrow, etc. in searching H. armigera larvae.
Gullbilled Tern, Whiskered Tern and River Tern were recorded feeding on the larvae of H. armigera on Chickpea in Gujarat.
The fruit of mulberry Morus Alba has very important ecological function to maintain insectivorous birds in the system. Fourteen species were recorded feeding on its fruits in Gujarat.
At least seven species of birds fed on the insect pests of Lucerne, particularly on H. armigera. The insectivorous birds that followed the laborers cutting Lucerne reduced about 91.7% of H. armigera in Gujarat. Only very small larvae escaped predation. The cutting of Lucerne at 24 days interval may not allow larvae to pupate and thereby discontinue the generation of H. armigera In wheat, the Rosy Pastor, Grey Wagtail, White Wagtail, Black Drongo and Bank Myna reduced about 34% H. armigera population in Gujarat2. Eighteen species of birds fed on the white grub, which were exposed during ploughing operation. Birds reduced 45 to 65% of grub population in Gujarat when the field was ploughed using bullocks on three consecutive days. Positive impact of bird predation on the next crop has been demonstrated. Laboratory experiments at Anand, Gujarat proved that Indian Myna, Cattle Egret and House Sparrow were capable of dispersing Bacillus popillae var. Holotrichiea causing milky disease in white grub (Holotrichia consanguineai. Indian Myna, Bank Myna and House Sparrow indiscriminately feed on the diseased larvae of H. armigera and help in the dispersal of Nuclear Polyhedrosis Virus (NPV). Page | 38
Birds picked up sawfly (Athalia proxima) maggots for 8 to 10 hours in a day with a success rate of 49 to 65%. The Cattle Egret regulated larval population of sawfly on mustard to an extent of 60% after irrigation, and brought down its population much below economic threshold level. Cattle Egret is the most important avian predator in the agricultural landscape and remains present during every agricultural operation to capture insect pests. Hence, it should be given due importance in the IPM programme. The species can be encouraged to breed on thorny trees at the edges of village ponds near human settlements. At Ludhiana Common Myna and Bank Myna significantly checked the larval population of H. armigera in the standing crop of Berseem fodder. At Kota, Rajasthan, the House Sparrow reduced H. armigera population by 20 to 40% in chickpea. Gullbilled Tern is reported for the first time to feed on Helicoverpa larvae and grasshoppers from the pearl millet fields of coastal Gujarat. Bank Mynas breeding in Jamnagar fed its nestlings mostly with insect matter and it brought food to its nest at an average on 7 times per hour. At KAU, 14 spp of insectivorous birds controlled the rice insect pest and recorded higher yield in experimental plot (3105 kg/ha) than the control (1780 kg/ha). In Andhra Pradesh species recorded during pre and post agricultural activity on different crops showed variations in their compositions. The feeding guild structure of birds in these crops revealed high occurrence of insectivorous birds followed by omnivorous and granivorous. This indicates that insectivorous birds play a significant role in different crops in controlling various insect pests. In Pigeon pea several components of BIPM modules were tested individually at ARS, Tandur in Andhra Pradesh. The data obtained clearly suggested that least incidence of pest and extent of damage by the pest was observed in the treatment where NPV + Bird perches were employed. Similarly more yields were recorded in the above treatment (1475 kg/ha) while in NPV (1450 kg/ha) & (1462 kg/ha) Bird perches than the control (868 kg/ha). A total of24 species of insectivorous birds were found to utilize the crop during the season and the percent abundance was varied (5.2 to 21.21%) in different months. Among these birds, 15 species were utilized significantly (15.78 to 94.73) the artificial bird perches and helped in controlling the pests.
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In Anand, the IPM module consisting of HDP net, T-shaped perches and T-shaped perches with NPV were used to control H. armigera larvae, from which T-shaped with NPV proved effective to check the population of H. armigera over control. The population of medium size larva was significantly lower in perch + NPV treated plot as compared to other treatment followed by perch alone than other treatment. More or less similar trend was observed for the large sized larvae also. 3 species of birds viz., Common myna Acridotheres tristis, Common swift Apus affinis and cattle egret Bubulcus ibis observed feeding voraciously and reduced 20 to 30%, of Swarming caterpillar larvae, stem borer pupae and grasshoppers in harvested paddy fields at Kerala. In Punjab, in cotton the artificial 'T' perches followed by sorghum/millet perchings outperformed in their utilization than other perching facilities with respect to mean no. of visits performed by birds to be 4.00 to 9.27 ± 5.10 and 1.00 to 2.80 ± 1.17 per 20 minutes respectively for picking up the insects. Relatively less number of bird species utilized 'T' perches and perching/facilities in sprayed fields. Maximum utility of perches was by 8 species in August-September which corresponded with increased foliage density and corresponding increase in insect infestation intensity. In castor, 16 spp. of birds controlled 36% of Spodaptera litura, while in Kerala Crow pheasant Centropus sinensis devoured 5% of stem borer larvae in cardamom and termites were voraciously fed by common crows.
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During the outbreak of army worm in the rice fields, cattle egret, house crow and other insectivores birds were very active in feeding the larvae. The feeding potential of cattle egret was 408, third/fourth instar larvae per hour. In tomato, crop 11 species of insectivorous birds reduced 25% of Helicoverpa armigera larvae, while in chickpea 8 species of birds reduced 20- 23% of Helicoverpa armigera larvae4. Similarly, in cucurbits viz; Muskmelon, Watermelon and Bitter gourd, the artificial perches could attract 6, 8, 8 species out of total 8, 11, 13 species visiting the crops. For the first time in the country, standardized the nest boxes design for cavity nesting birds in controlling insects & rodent's pests of various crops. 55% of nest boxes was preferred by house sparrow Passer domesticus, common myna Acridotheres tristis and spotted owlet Athene brama that were installed at different places in Andhra Pradesh and Punjab3. Wooden nest boxes were readily accepted and adopted for breeding by Common myna Acridotheres tristis and spotted owlet Athene brama which resulted in 68.32% breeding success in Common myna Acridotheres tristis. While earthen pots with lids were adopted by House sparrow and Indian robin Saxicoloides folicata and egg laying was recorded in 22.06 and 1.47% pots, respectively. Egg laying by Common myna Acridotherestristiswas accomplished in three successive layings 62.74, 27.45 and 17.65% after successfully rearing of the previous brood in wooden nest boxes. Page | 41
The standard size having 30 cm height (depth) x 23 cm width with an opening of 7.5 cm at a height of 12.7 cm on the front cover of the box and with a lid (roof cover) of 25 cm x 32 cm with provision of two hinges at the top of the back cover for hanging/ fixing boxes on the trees, has been recommended for Common Myna (Acridotheres tristis), Indian Roller (Coracias benghalensis), Indian Robin (Saxicoloides fulicata), Indian Gray Hornbill (Tockus birostris), Collared Scops-owl (Otus bakkamoena), Spotted Owlet (Athene brama) and Magpie Robin (Copsychus saularis).
Soil digging activities along the roadside in Gujarat, particularly vertical side of the land immediately attracts the cavity nesting birds like Bank Myna Page | 42
Acredotheres ginginianu, Small Green Bee-eater Merops orientalis, Bluetailed Bee-eater Merops philippines and Spott Owlet Athene brama.
Food samples of spotted owlet were analysed and found high occurrence rodent remnants (60%) in winter followed insects remnants (24%). However, in summer and monsoon the insect diet was predominantly high (58 & 35%) when compared to rodents. The difference may be due to high occurrence of rodents during winter in relation to crop stages can be attributed as a reason for more rodent remnants. In food of the Spotted, Owlet additional food items identified for the first time were: appendages of the scorpions, Bufo melanosticus and remnants of bats. The comparative studies on feeding behavior of 3 spp of Owls namely Barn Owl, Tyto Alba, Fish eating Owl, Bubo flavipes and Spotted Owlet Athene brama in Kerala revealed that rodent remnants (82%) in Barn Owl diet, Crab remnants (65%) in Fish Owl and Insecta (60%) in Spotted Owlet were predominantly found throughout the season. Barn Owl (Tyto alba) feed largely on nine species of rodents, which includes Common Shrew (Suncus murinus), House Rat (Rattus rattus), House Mouse (Mus musculinus), Five-stripped Squirrel (Finambulus pinnantii), Lesser Mouse-tailed Bat (Rhynopoma hardwickii.), Among identified species maximum was Suncus murinus (27.06%) followed by Bandicota bengalensis (15.12%) while minimum species was found Vandeleuria oleracea (0.27%).
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The Bank Myna Acridotheres ginginianus fed 1061 g of insects, which were about 3810 in number during the nestling period of a brood with two nestlings at Jamnagar. The dietary preference and diet composition of Cattle egret Bubulcus ibis in different heronries of Andhra Pradesh showed that high preference to insects (75%) followed by non-insect matter (25%). This indicates, the cattle egret is an important potential depredatory bird in agricultural eco-system in controlling insect pests. In Gujarat, diet analysis of harriers largely consists of 60-70% Orthopterans (Grassbopers) Insects. Sindh Sparrow (Passer pyrrhonotus) is being reported for the first time, from central Gujarat and found feeding on the Salavadora persica. In Andhra Pradesh, for the first time, Ashy wren warbler (Prinia socialist was observed nesting in cotton crop and feeding nestlings with available larvae within the cropped area. Presence of fruit bearing trees like Butea monosperna, Pithecolobium dulce, Morus Alba, Ficus benghalensis, Cordia gharaf and Salvadora persica around farm lands attracted 18 species of insectivorous birds and helped in controlling crop pests to the extent of 40 to 63%.
Range extension of Isabelline chat (Oenanthe isabelline) was reported for the first time, at ARS, Tandur, Rangareddy district of Andhra Pradesh and found feeding voraciously on Helicoverpa armigera in Pigeon pea crop.
In Eastern Ghat of Andhra Pradesh, for the first time recorded the range expansion of Southern Trogon (Harpactes foeciatus) a new record.
Total 494 Sarus Cranes were counted in Anand and Kheda districts. In the population there were 19% juveniles which indicated successful breeding in the preceding monsoon 5. Page | 44
In Andhra Pradesh, out of 184 villages surveyed 60 villages were found with occurrence of sporadic populations of house sparrow. The % occurrence of house sparrow was significantly reduced in South zone and Krishna Godavari Zone with a flock range of 4 - 11 birds. The occurrence of these species is mainly restricted to village habitats. The main reason for decline of these species is attributed to loss of preferred habitat, high use of insecticides and pesticides and other changes in the socio economic conditions in the rural areas. Analysis of Peafowl habitat revealed the occurrence of 15 and 24 species of trees, weeds, bushes/grasses, 29 and 18 species of birds and burrows of porcupine in reserve forest and semi forest area respectively. Peafowl damage was mainly by browsing of leaves in wheat, paddy, fodder and oil seed crops which little effected the survival of plants whereas browsing resulted in complete loss of plants in vegetable crops. Selfdefending or employing labour for yelling, scaring by throwing stones, fencing of fields by blocking intruding points of fowls, installing scare crow with raised arm with stick in hand and keeping pet/hunter dogs are the main methods being followed by farmers for management of Peafowl. Present Status of Birds in Agriculture Lands The application of pesticide in agriculture land leads most of the common birds to the verge of extinction (e.g. Sarus Crane, House Sparrow). Moreover in recent days farm lands are turned as bird hunting yards UN precedential and uncontrolled bird hunting in agricultural lands increased in Page | 45
an alarming manner. Especially the more people in delta districts are turning as consummate bird hunters and they are using different equipments and shot guns for killing the birds the very good market is there for the poached birds in this region. Numbers of hotels in this area are regularly purchasing the birds from the poachers. Even the birds are available in the nearby slaughter houses and fish markets unfortunately the hunters target the most beneficial species such as Cattle Egrets, Bitterns, Herons, Sandpipers and Storks. Especially the Cattle Egrets are the highly targeted species in the delta districts. The hunting reaches its peak during rainy season, ploughing periods and weekends. The uncontrolled killing of this species might have a palpable effect on agriculture and might lead to frequent pest outbreaks. References 1.
Ali S. Bird friends and foes of the cultivator. Indian farming. 1949; 10:385-387.
2.
Basappa H. Biodiversity of bio control agents in sunflower ecosystem. Journal of Biological Control. 2011; 25(3):182-192.
3.
Laxmi narayana B, Vasudev Rao V. Avifaunal assemblages in relation to different croplands/habitats of nalgonda district, andhra pradesh, India. International Journal of Life Sciences Biotechnology and Pharma Research, 2013, 2:3.
4.
Mehta KS, Patyal SK, Rana RS, Sharma KC. Eco friendly techniques for the management of Helicoverpa armigera (Hubner) in tomato. Journal of Bio pesticides. 2010; 3:296-303.
5.
Paliwal1 GT, Bhandarkar SV. Observation on the Biodiversity Conservation of Birds in Paddy Agro Ecosystem in Different Crop Stages. Int. J Curr. Microbiol. App. Sci. 2014; 3(9):1161-1165.
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Chapter - 4 Pesticide use ill Effects in Relation to Invertebrates and Vertebrates
Authors Nagamandla Ramya Sri Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India Nagulapally Sneha Latha Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India Gautam Kunal Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India Venisetty Punnamchander Department of Entomology, Faculty of Agriculture, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad, Telangana, India
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Chapter - 4 Pesticide use ill Effects in Relation to Invertebrates and Vertebrates Nagamandla Ramya Sri, Nagulapally Sneha Latha, Gautam Kunal and Venisetty Punnamchander
Introduction Pesticides are a major factor affecting biological diversity, along with habitat loss and climate change. They can have toxic effects in the short term in directly exposed organisms, or long-term effects by causing changes in habitat and the food chain. Many pesticides are toxic to beneficial insects, birds, mammals, amphibians and fish. Pesticide poisoning depends on pesticide’s toxicity and other properties like water solublity, quantity applied, frequency, timing and method of spraying, weather, vegetation structure, and soil type. Insecticides, rodenticides, fungicides and the more toxic herbicides threaten the exposed life. Over the past 40 years, the use of highly toxic carbamate and organophosphate has strongly increased. In the south India use of organochlorines such as endosulfan, which is highly persistent in the environment had effected several lifes. In Canada, losses among 62 imperilled species were significantly more closely related to rates of pesticide use than to agricultural area in a region. Species loss was highest in areas with intensive agriculture (aerial spraying).The authors concluded that either pesticides, or other features of intensive agriculture linked to pesticide use in Canada, played a major part in the decline of imperilled species. Pesticides affect wildlife directly and indirectly via food sources and habitats. Wildlife poisoning by highly toxic insecticides, rodenticides, fungicides (on treated seed) and toxic herbicides can cause major population decline. Pesticides accumulating in the food chain, particularly those which cause endocrine disruption, pose a long-term risk to mammals, birds, amphibians, and fish. Page | 49
Broad-spectrum insecticides and herbicides reduce food sources for birds and mammals. This can produce a substantial decline in rare species populations. By changing vegetation structure, herbicides can render habitats unsuitable for certain species. This threatens insects, farmland birds, and mammals. Ideally a pesticide must be lethal to the targeted pests, but not to nontarget species, including man. Unfortunately, this is not the case, so the controversy of use and abuse of pesticides has surfaced. The rampant use of these chemicals, under the adage, “if little is good, a lot more will be better” has played havoc with human and other life forms. A WHO study, which analyzed food samples across India, found that 50 per cent were contaminated with pesticide residues, with 30 per cent exceeding permissible limits. Contents Impact of Pesticides on Butterflies, Bees, and Natural Enemies Broad-spectrum insecticides (e.g. carbamates, organophosphates and pyrethroids) can cause population declines of beneficial insects such as bees, spiders, or beetles. Many of these species play an important role in the food web or as natural enemies of pest insects. Since 1970, insect numbers in cereal fields in Sussex have dropped by half Numbers of bugs, spiders and beetles were considerably higher in untreated fields. On British organic farms, numbers and species richness of butterflies was greater than on conventional farms. The number of carabid beetles and spiders was usually higher on organic farms. Conventional management practice appeared to affect natural enemies far more than other insects or target pests. Moths were considerably more abundant on organic farms and species richness was higher. In arable fields, insecticide use was an important factor influencing communities of spiders. On sites with an increased pesticide input, communities of bugs, wild bees, and spiders were more uniform, indicating less exchange between communities in areas with intensive agriculture. Bees perform essential pollination. Honey bees are under pressure from parasitic mites, viral diseases, habitat loss and pesticides. Intensified agricultural practices, habitat loss, and agrochemicals are considered to be among the chief environmental threats to Europe’s honey and wild bees. Agricultural policy must reduce these pressures to ensure adequate pollinator populations. On organic farms in the USA, near natural habitat, diverse native wild bee communities provided full pollination services, while Page | 50
diversity and numbers of native bees were greatly reduced on other farms. In the UK, of the 95 incidents of bee poisoning (where the cause could be identified) between 1995 and 2001, organophosphates caused 42%, carbamates 29%, and pyrethroids 14% of cases. In the last decade in the UK, insecticides which poisoned bee colonies included bendiocarb (a carbamate) and three pyrethroids: cypermethrin, deltamethrin and permethrin. Synergistic effects between pyrethroids and EBI fungicides (imidazole or triazole fungicides) can increase the risk to honeybees (Pilling & Jepson 2006). Clothianidin, and to a lesser extent, imidacloprid are highly toxic to bumble bees and other wild bees. These two neonicotinoid insecticides are used to treat corn and sunflower seeds. In 2008, clothianidin caused many bee poisonings and colony deaths in southern Germany. The product has since been withdrawn. When imidacloprid-treated seed is grown, a large enough amount can enter the environment to poison bees. Residues of imidacloprid in maize pollen grown from treated seed can be a high risk to bees owing to sublethal effects. Even at low doses of imidacloprid, negatively affect bee foraging behaviour. Exposure to low doses of imidacloprid over a longer period led to reduced learning capacity among bees. In alfalfa, imidacloprid affected the number and species diversity in communities of arthropods (natural enemies such as spiders) more strongly than among target pest insects. Imidacloprid has been banned in France. Field margins without use of pesticides (herbicides in particular) had a positive effect on the number of Lepidoptera (such as moths or butterflies), bugs, and staphylinid beetles at the edges of arable fields. In organic plots, average numbers of spiders and carabid or staphylinid beetles were almost twice as high as those in conventional plots. Pesticides which are highly toxic to bees, bumblebees and other beneficial insects: carbamates (e.g. aldicarb, benomyl, carbofuran, methiocarb), organophosphates (e.g. chlorpyrifos, diazinon, dimethoate, fenitrothion), pyrethroids (e.g. cyfluthrin, cyhalothrin), and neonicotinoids (imidacloprid, thiamethoxam, clothianidin). Recently, clothianidin used in seed treatments have caused widespread bee poisoning. Imidacloprid residues in plants can negatively alter bee behaviour.
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Pesticide ill Effects on Natural Enemies Indirect Effects of Pesticides on Natural Enemies Although indirect effects may be more subtle or chronic compared to direct effects any indirect effects may inhibit the ability of natural enemies to establish populations, they suppress the capacity of natural enemies to utilize prey, effect parasitism (for parasitoids) or consumption (for predators) rates; decrease female reproduction, reduce prey availability, inhibit ability of natural enemies to recognize prey, influence the sex ratio (females: males), and reduce mobility, which could impact prey-finding. In addition, more than one physiological and/or behavioural parameter may be indirectly affected after exposure to a pesticide. Furthermore, understanding the indirect effects of different concentrations of pesticides on fecundity, fertility, reproduction, adult and larva longevity, and prey consumption is important in successfully integrating natural enemies with pesticides and avoiding any indirect consequences on population dynamics 10. Systemic Insecticides Systemic insecticides, when applied as drenches or granules to the soil/growing medium, have been promoted to be relatively non-toxic to natural enemies due to lack of any direct exposure. However, this may not be the case as systemic insecticides may exhibit indirect effects on natural enemies via several mechanisms including elimination of prey, contamination of floral parts by the active ingredient, consumption of the active ingredient while ingesting plant fluids, and contamination of prey ingesting either lethal or sub-lethal concentrations of the active ingredient. Systemic insecticides, when applied to the soil or growing medium, may have minimal direct effects on aboveground natural enemies (both parasitoids and predators), however, they may indirectly influence natural enemies if mortality of prey populations is high (>90%). This results in a reduction or potential elimination of available prey that serve as a food source for natural enemies, making it difficult for natural enemies to locate any remaining individuals. This would then lead to a decline in natural enemy populations either through starvation or dispersal thus suppressing establishment. However, this effect is dependent on the foraging efficiency of the specific natural enemy. Furthermore, this may reduce the quantity or density of available prey or reduce their quality such that they are unacceptable as a food source for predators (both larvae and adults) or female parasitoids may not lay eggs. As such reproduction, foraging behaviour, fecundity, and longevity may be Page | 52
indirectly affected. The distribution of the systemic insecticide active ingredient into flower parts (petals and sepals) may indirectly impact natural enemies that feed on plant pollen or nectar as a nutritional food source including several species of predators such as minute pirate bug, Orius spp., which may feed on plants sometime during their life cycle and certain parasitoids. For example, adults of the parasitoid, Anagyrus pseudococci were indirectly affected after feeding on nectar of buckwheat (Fagopyrum esculentum) plants that had been treated with a soil application of a systemic insecticide. Stapel et al. (2000) found that foraging ability and longevity of the parasitioid, Microplitis croceipes was reduced after feeding on the extra floral nectaries of cotton (Gossypium hirsutum) plants that had been treated with systemic insecticides. It was also noted that the application method (soil vs. foliar) and possibly timing of application (spatially and temporally) may have indirect effects on parasitoids that feed on flower pollen and nectar as a food source. In addition, foraging behaviour may be altered depending on the exposure time and concentration of active ingredient present in floral portions of plants. As such, indirect effects associated with systemic insecticides may reduce the overall success of parasitoids in regulating arthropod pest populations under field conditions. Translocation of systemic insecticides into flowers may indirectly affect natural enemies by altering foraging behavior as has been shown with the pink lady beetle, Colemegilla maculata, the green lacewing, Chrysoperla carnea, and the parasitoid, A. pseudococci. Nevertheless, the ability of systemic insecticides, when applied to the soil or growing medium as a drench or granule, to move into floral parts may be contingent on water solubility, application rate, and plant type 6 . In addition, the metabolites of certain systemic insecticides, which in general, may be more water soluble and toxic to arthropod pests, could be more concentrated in pollen and nectar than the actual active ingredient. This might have a significant indirect effect on natural enemies. In fact, the metabolites associated with certain systemic insecticides have been implicated to indirectly affect natural enemies, primarily by contaminating flower pollen or extrafloral nectories as the active ingredient is translocated and distributed throughout plant parts. Furthermore, any natural enemies feeding on prey that have fed upon plants and have ingested concentrations of the systemic insecticide active
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ingredient may be indirectly affected. This is associated with prey contamination, which can lead to subtle and long-term indirect effects on parasitoids and/or predators. Insect Growth Regulators Insect growth regulators are compounds that are active directly on the immature stages (larvae or nymphs) of certain insect pests, and there are three distinct categories of insect growth regulators: juvenile hormone mimics, chitin synthesis inhibitors, and ecdysone antagonists. Insect growth regulators have been presumed to be compatible, with minimal indirect effects on natural enemies, and numerous studies have evaluated the indirect effects of insect growth regulators on natural enemies, both parasitoids and predators, under laboratory and field conditions. However, there is distinct variability regarding the indirect effects of insect growth regulators on natural enemies, which is primarily associated with natural enemy type (parasitoid or predator), kind of insect growth regulator, life stage evaluated, and timing of application (spatially and temporally). Pyriproxyfen
Pyriproxyfen, a juvenile hormone mimic was demonstrated to have no indirect harmful effects on adult female oviposition and egg viability of the green lacewing, C. carnea.
Similarly, pyriproxyfen exhibited no indirect effects on development time, female longevity, and fertility of an Orius sp. after exposure under laboratory conditions.
Pyriproxyfen did not negatively affect parasitism capacity of the parasitoid, Aphytis melinus and there were no indirect effects on the sex ratio of the progeny whereas female Coccophagus lycimnia failed to produce any progeny.
However, exposure to pyriproxyfen delayed development and decreased the parasitization rate of the parasitoid, Hyposoter didymator.
In addition, pyriproxyfen has been demonstrated to substantially alter the development time of Chrysoperla rufilabris immatures whereas pyriproxyfen did not indirectly impact Delphastus catalinae female fecundity after adults had fed upon treated eggs of the sweet potato whitefly, Bemisia tabaci.
In another study, exposure of Podisus maculiventris fifth instars to pyriproxyfen did not result any indirect effects on reproduction. Page | 54
The parasitoid species may influence any indirect effects as both Encarsia pergandiella and Encarsia transvena were not indirectly affected after exposure to pyriproxyfen whereas Encarsia formosa exhibited reduced emergence rates, increased development time, and decreased parasitization when exposed to different concentrations of pyriproxyfen.
This demonstrates that the parasitoid species, natural enemy type, and developmental life stage may influence the extent of any indirect effects of insect growth regulators.
Kinoprene
Another juvenile hormone mimic insect growth regulator, kinoprene, has been shown to be indirectly harmful to natural enemies by inhibiting adult emergence of the leafminer parasitoid, Opius dimidiatus and the aphid parasitoid, Aphidius nigripes.
Although directly harmful to the parasitoid, Leptomastix dactylopii, kinoprene did not indirectly affect percent parasitoid emergence from citrus mealybug (Planococcus citri) mummies.
Nevertheless, kinoprene may inhibit adult emergence when applied to prey parasitized with larval or pupal stages of certain parasitoids.
Fenoxycarb
Fenoxycarb is a juvenile hormone analog that has shown to be indirectly harmful to certain natural enemies.
For example, different concentrations of fenoxycarb delayed the development time from pupae to adult of C. rufilabris, and significantly delayed development of third instar larvae but not first instar larvae.
In addition, female reproduction was inhibited when second and third in stars were initially exposed to fenoxycarb.
Fenoxycarb (at various concentrations) increased duration of larval development of the tachinid parasitoid, Pseudoperichaeta nigrolineata, and Bortolotti observed a similar response (increased longevity) for the third instar larvae of C. carnea.
Exposure to fenoxycarb indirectly affected female longevity and fecundity of the predator, Micromus tasmaniae.
Cyromazine
Cyromazine is an insect growth regulator that disrupts molting by Page | 55
affecting cuticle sclerotization through increasing cuticle stiffness in insects and has been shown toexhibit indirect effects on the reproduction of Phytoseiulus persimilis females whereas no indirect effects, associated with adult emergence rates, were exhibited after the parasitoid, Chrysocharis parksi was exposed to cyromazine.
Furthermore, exposure to cyromazine did not indirectly affect longevity and reproduction of the leafminer parasitoids, Hemiptarsenus varicornis and Diglyphus isaea.
Diflubenzuron
Another insect growth regulator, diflubenzuron, which is a chitin synthesis inhibitor, has been shown, in general, to have minimal indirect impact on natural enemies-both parasitoids and predatorsunder laboratory and field conditions.
However, exposure to diflubenzuron decreased female longevity and reduced the parasitization rate of the end oparasitoid, Hyposoter didymator and reproduction of the parasitoid, Eulophus pennicornis.
It was reported by that M. tasmaniae, when exposed to diflubenzuron, resulted in indirect effects on reproduction, sex ratio (female bias), and longevity.
In contrast, diflubenzuron exhibited no indirect effects on the reproduction of Podisus maculiventris adults.
Additionally, diflubenzuron displayed minimal indirect effects on the parasitoid, Macrocentrus ancylivorus.
Similar to other insect growth regulators, any indirect effects of diflubenzuron are likely associated with the natural enemy type, timing of application (spatially and temporally), and exposure time.
Buprofezin
Buprofezin, a chitin synthesis inhibitor, has been shown to sterilize certain natural enemies, and reduce the number of progeny produced per female and alter sex ratios.
In addition, feeding on buprofezin-treated sweet potato whitefly (B. tabaci) eggs resulted in a decrease in female fertility and fecundity, and sterilized the males of the predatory coccinellid, Delphastus catalinae indicating no compatibility with this insect growth regulator. Page | 56
Azadirachtin
Azadirachtin is an ecdysone antagonist, which may exhibit variability regarding any indirect effects on natural enemies.
It was reported by, for example, that azadirachtin inhibits oviposition of the green lacewing, C. carnea and indirectly affected both fertility and fecundity.
In addition, exposure to azadirachtin decreased longevity and predation rates, and inhibited prey finding.
Microbials
Although entomopathogenic fungi and bacteria (Bacillus thuringiensis) are, in general, not indirectly harmful to natural enemies, this may vary depending on concentration, natural enemy type, life stage exposed, timing of application (spatially and temporally), and environmental conditions (temperature and relative humidity).
The bacterium, B. thuringiensis has been shown to have indirect effects on certain parasitoids although this is dependent on the formulation.
Natural enemies may ingest fungal conidia when grooming (cleaning themselves) or when feeding on contaminated hosts; however, the extent of any indirect effects primarily depends on the concentration of spores present.
In addition, entomopathogenic fungi may indirectly affect certain natural enemies when feeding on prey that have been sprayed (contaminated prey). For example, larvae of the mealybug destroyer, Cryptolaemus montrouzieri were killed (50% mortality) after consuming mealybugs that had been sprayed with Beauveria bassiana. Moreover, exposure to B. bassiana reduced the fecundity of N. californicus females whereas the fungus Cephalosporium lecanii exhibited no indirect effects on longevity of the leafminer parasitoid, Diglyphus begini.
The micro-organism spinosad has been demonstrated to be indirectly harmful to a variety of predatory insects including the green lacewing, C. carnea ladybird beetle, Hippodamia convergens; minute pirate bug, Orius laevigatus; big-eyed bug, Geocoris punctipes; and the damsel bug, Nabis sp.Nevertheless,
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exposure to spinosad did not inhibit foraging behavior and reproduction of P. persimilis females.
It has been shown by that parasitoids may be indirectly affected by spinosad based on decreased reproduction and reduced longevity. However, exposure to spinosad did not indirectly affect the sex ratio of the parasitoids, Aphytis melinus and L. dactylopii, and there was no significant effect on reproduction and longevity of L. dactylopii females.
Fungicides
It was determined that the ‘newer’ fungicides, azoxystrobin and fosetyl-aluminum did not inhibit prey consumption (fungus gnat larvae) of rove beetle, A. coriaria adults under laboratory conditions.
Bostanian et al. (2009) reported that none of the fungicides evaluated including myclobutanil, propiconazole, fenhexamid, and pyraclostrobin, had any indirect effects on the fecundity of the predatory mite, G. occidentalis, and the fungicides captan, mancozeb, and myclobutanil did not indirectly affect longevity and fecundity of A. fallacis females.
Exposure to the fungicides boscalid and kresoxim-methyl, which are relatively ‘newer’ fungicides did not indirectly affect fecundity of both E. victoriensis and G. occidentalis; and found that exposure to the fungicides myclobutanil and trifloxystrobin resulted in no indirect effects on fecundity of G. occidentalis.
Effects of Pesticides on Aquatic Organisms Effects of Pesticides within the vital systems of the body of the Exposed object which are divided into the following based on the position of impact. On Acetylcholinesterase (ACHE): ACHE activity is more sensitive for organophosphate and car bam ate pesticides than other contaminants, but the inhibition of this enzyme have been also used to indicate the exposure and effects of other contaminants in fishes. It has been shown that the addition of crude oil to brain homogenate in a mounts equivalent to sediment concentration inhibit ACHE activity in fish. Both brain ACHE and muscle were inhibited in fish reared in areas heavy polluted with PA, heavy metals and pesticides. Reduction of swimming performance and peroxidative damage in brain and gills occurred in fish exposed to prolonged exposure to organophosphate 2. Page | 58
Chromosomal Aberrations and Carcinogenic Effects: Dichlorvos at concentrations of 0.01 ppm caused chromosomal aberrations in the form of centromeric gaps, chromatid gaps, chromatid breaks, sub-chromatid breaks, attenuation, extra frage ments, pycnosis, stubbed arms etc in kidney cells of Channapunstatus fish after exposure periods of 24, 48, 72 and 96 hrs. Also, toxicity with Diclorvos has been related to alterations in DNA replication, which cause mutations and cellular hyper proliferation as a result of local mutation. Effect on Protein Contents: Appreciable decrease in protein level of liver, muscle, intestine, gills and blood of fish (Channa p.) exposed to Oleondrin, Cyprinuscarpio fish exposed to Endosulfan. Effects of Pesticides to Salmonid Fish: The long term exposure to certain pesticides can increase stress in juvenile salmonids and thereby render them more susceptible to predation. Pesticides alter swimming ability, which in turn can reduce the ability to feed, to avoid predators, to defend territories, and to maintain position in the river system. Effect on Immune System and Endocrine Disruptors: Exposure to low concentrations of pesticides can disrupt the immune system of fish. Pesticides at low concentrations may act as mimics or blockers of sex hormones, causing abnormal sex development, feminization of males, abnormal sex ratios, and unusual mating behaviour. Pesticides can indirect affect fish by interfering with food supply or alternating habit. Toxicity of Pesticides to Cyprinid and Catfish: Aldrin, dieldriny, DDT, HBC and Chlordan (for 10, 20, 30 days/carp fish) increased hemoglobin content and increased PCV. Synthetic pyrethroid (LC50 for 24, 48, 72 and 96 hrs/carp and cat fish), induced swimming behaviour was in crock screw pattern and rotating along horizontal axis andfollowed by "S" jerks sudden rapid and non-directed sport of forward movement likely to be busted swimming Respiratory disruption. Change in color of the gill lamellae from reddish to light brown. Excessive coagulated mucus on gills also accumulated. Hyperactivity, zigzag movement, loss of buoyancy, elevated cough, loss of schooling behavior, swimming near the upper surface (Gasping). Increased mucous secretion, flaring of the gill arches and covers, head shaking and restlessness before death also, induced. Malathion, with Ham fish, this pesticide induced reduction in ovarian weight, retardation growth of the pre-vitellogenic oocytes (low doses). In high doses: degeneration of the immature oocytes and rupture of the follicular epithelium and disturbance in the endocrine /hormonal imbalance. Carbofurane at 0.5,
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1and 2mg/l in catfish induced degeneration of the follicular walls, connective tissues and vacuolization in the ooplasm of the stage II and III oocytes. Malathion (1.2 mg/l-catfish) induced changes in ovigerous lamella, clumping of cytoplasm, Degeneration in the follicular cells, Shrinkage of nuclear materials, increased atretic oocytes, and Ruptured follicular epithelium. Malathion, catfish (LC50 for 96 hour (0.98 ppm) induced adhesion and cytoplasmic retraction in oocyte, Degeneration and increased in the number of the atretic oocytes, Damage to oocytes, Cytoplasmic retraction and clumping of the oocytes. Partial destruction of the ovigerous lamellae and vitellogenic membrane also were occurred. Diazinon (Organophosphorus compound) with Bluegill fish induced adhesion of the primary follicles, Cytoplasmic retraction in oocyte II, Cytoplasmic degeneration, increased follicular spaces and vacuolated cytoplasm, Extrusion of karyoplasms and necrosis in the cytoplasm. Endosulfan, catfish induced decreased the activity of citrate synthesis (CS) and G6-PDH in the brain, liver and skeletal muscles of freshwater cat fish, Impairment of metabolism in fish, which appeared to be due to inhibition of transcription. Methyl parathion (1-10 ppm) with Catla fish increase in opercular movement, loss of equilibrium, irregular swimming activity, rapid jerky movement, frequent surfacing, change in body color, increased mucus secretions and 50% mortality. Dichlorvos (o.65, 0.90 and 1.17 mg/l) with common carp fish induced decrease in Gonad somatic index (GSI), and ovaries showed histopathological disordered. Pyrethroid at 0.4 µg/l with carp fish fingerlings induced erratic and darting swimming movements, Excess accumulation of ACH in the cholinergic synapses leading to hyperstimulation, and Respiratory distress 8. Pesticide Toxicity to Non-Target Aquatic Micro-Organisms Pesticide Toxicity to Non-Target Aquatic Microorganisms Microorganisms are important inhabitants of aquatic ecosystems, where they fulfill critical roles in primary productivity, nutrient cycling, and decomposition. Microorganisms span three kingdoms, including > 50,000 different species of bacteria, algae, fungi, and protozoa. They cover a tremendous range of size classes and morphologies, exist in every habitat, and include multiple feeding types, mobile, and non-mobile forms, and a variety of reproductive strategies and growth rates. The majority of the available pesticide studies regarding aquatic microorganisms describe effects on algae. Studies of herbicide effects dominate, in particular effects caused by atrazine. Far fewer pesticide studies exist for aquatic bacteria, fungi, and protozoa. The mechanism of pesticide action in microbial species may not be Page | 60
the same as for the target-organisms. In microorganisms, pesticides have been shown to interfere with respiration, photosynthesis, and biosynthetic reactions as well as cell growth, division, and molecular composition5. Insecticides Few studies address direct toxic effects of insecticides to aquatic microorganisms. However, the toxicity of the two carbamate insecticides carbaryl and carbofuran to algae and cyanobacteria were tested in expected environmental concentrations (EEC) by Peterson et al. (1994). The EEC is a concentration estimate of a worst-case exposure scenario for an aquatic habitat in a lotic system, based on the input of the maximum proposed application rate. Peterson et al. (1994) showed that growth inhibition, following carbaryl exposure (3.7 mg/L), ranged from 35% to 86% with the cyanobacteria Pseudanabaena and Anabaena inaequalis being the most sensitive species tested. Actually, >50% inhibition was found in nine of the ten species included in the study. In contrast, carbofuran had relatively low toxicity to most species tested when applied at the EEC of 0.67 mg/L. Also the organophosphorus insecticides fenitrothion and pyridaphenthion cause growth inhibition in algae and cyanobacteria. The EC50 (96 h) for fenitrothion and pyridaphenthion ranged from 0.84 to 5.5 mg/L for the green algae Scenedesmus acutus, Scenedesmus subspicatus, and the cyanobacteria Pseudanabaena galeata and from 5.7 to 30.9 mg/L for the green algae Chlorella vulgaris and Chlorella saccharophila. Scenedesmus acutus was the most sensitive species for both insecticides and its EC10 (96 h) range from 0.14 to 0.32 mg/L, which is lower than the concentrations found in natural waters. In contrast to single species tests, Delorenzo had tested the effects of the agricultural insecticides endosulfan and chlorpyrifos on an estuarine microbial food web. Endosulfan was primary found to target the phototropic portion of the bacterial community, i.e. the cyanobacteria4. Total bacterial abundance, but not heterotrophic bacterial productivity, was reduced with endosulfan treatments of 1 and 10 µg/L. Cyanobacterial taxa like Melosira and Oscillatoria were among those that were eliminated from the highendosulfan treatment. In the same study, chlorpyrifos affected many of the phototrophic endpoints tested, e.g. both chlorophyll a, and the phototrophic bio volume were reduced in 1 and 10 µg/L. Several diatom genera (Asterionella, Bacillaria, Gomphonema, and Tabellaria) present in the controls were absent in the 10 µg/L treatment and heterotrophic ciliates and flagellates were reduced. In contrast, the bacterial abundance increased significantly compared to the control when chlorpyrifos was added. Page | 61
However, the changes in the chlorpyrifos treatments occurred mainly in the high dose (10 µg/L). Herbicides Peterson had tested the growth inhibition of green algae (Scenedesmus quadricauda and Selenastrum capricornutum), diatoms (Nitzschia sp. and Cyclotellameneghiana), and cyanobacteria (Microcystis aeruginosa, Oscillatoria sp., Pseudoanabaena sp., Anabaena inaequalis and Aphanizomenonflos-aquae) in response to exposure of 23 different pesticides in EECs. Each of the five triazine herbicides tested (atrazine, cyanazine, hexazinone, metribuzin, and simazine; 2.7-2.9 mg/L) and diquat (0.7 mg/L) caused > 50% inhibition of growth in all test species. Later studies by Peterson et al. (1997) showed that already 5% of the EEC of hexazinone (0.14 mg/L) inhibited growth more than 80% in both diatoms and green algae. In addition, 0.7-14% of the EEC of diquat (0.005-0.1 mg/L) caused a 50% inhibition of diatoms and cyanobacteria 9 The earlier study by Peterson et al. (1994) also revealed that glyphosate (2.8 mg/L) was highly toxic to diatoms and thenitrogen-fixing cyanobacterium Anabaena flos-aquae at EECs, but relatively non-toxic to the remaining algal species. Fungicides According to Delorenzo there is very little information available about agricultural fungicide toxicity to aquatic microorganisms. Knowledge about fungicide toxicity in low concentrations is even scarcer5. However, in a single species test Peterson9 compared the sensitivity of ten algal species to the triazole derivative fungicide 13 propiconazole. At the EEC of 0.08 mg/L, inhibition of 14C uptake was80%) and an estimated 36% of the population lives below the poverty line. The climate is typically subtropical, with hot and humid summers and severe monsoons followed by mild winters. The region receives heavy rainfall (2–3 m annually), on account of extended monsoons, beginning with pre-monsoon activity during March/April and maximum precipitation during May to September/October. The high relative humidity (60-80%) throughout the year is conducive to proliferation and longevity of disease vectors, permitting active transmission of the causative parasites. Mosquitoes represent one of the most challenging groups of insects to mankind. It has well established itself as the carriers of several deadly diseases such as malaria, dengue, lymphatic filariasis and viral diseases. The container- breeding mosquitoes of the subgenus Stegomyia, primarily Aedes aegypti (L) (renamed as Stegomyia aegypti) and Ae. albopictus (Skuse) (renamed as St. albopicta) (Diptera: Culicidae), represent a major threat to health in South-East Asia as they are efficient vectors of significant arboviruses such as dengue, yellow fever and Chikungunya 1, 2, 3, 4, 5. Historical Background of Dengue Dengue fever is an ancient viral infection with potential disastrous complexities. The earliest record found to date is in a Chinese Encyclopaedia of disease, symptoms and remedies, edited in 610 A.D and again in 992 A.D 6 . The word "Dengue" is taken from the Swahili expression Ka-dinga pepo signifying "cramp like seizure". The primary clinically recognized dengue epidemic happened in the 1780s at the same time in Africa, Asia and North America. Benjamin Rush, who authored the expression "break bone fever" on account of the manifestations of myalgia and arthralgia is likewise credited to the first clinical case report dates from 1789 epidemic in Philadelphia (USA). The term dengue fever came into general use after 1828. With the expansion of shipping and growth of port cities in the 18th and 19th centuries the mosquito vector, Aedes aegypti and the dengue viruses spread to new geographic areas causing major epidemics. After the Page | 108
World War II, fast urbanization in Southeast Asia prompted expanded transmission and hyper-endemicity. Dengue infection was first reported in Japan in 1943 by immunization of serum of patients in suckling mice 7. The infection was separated from sera of US fighters at numerous parts of the World including Kolkata amid 1944 8. The significant epidemic of the DHF happened in 1953-1954 in Philippines took after by a quick worldwide spread of epidemics of DF/DHF 9. Dengue Fever and Dengue Haemorrhagic Fever Dengue is prevalent in more than 100 countries and threatens the health of more than 2.5 billion people, living in tropical and subtropical regions of the world 10. Dengue is the cause of an estimated half a million hospitalizations each year with some 24,000 death each year and enormous economic losses. Dengue is caused by four antigenic ally related virus serotypes which are dengue type 1, 2, 3 and 4 viruses. The dengue virus is in the genus Flavivirus 11. There are three types of dengue fever, namely classical dengue fever (DF), dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) 12. The term “haemorrhagic fever” was first applied to illness in South-East Asia especially Philippines in 1953 13. Dengue is transmitted by the bite of a mosquito contaminated with one of the four dengue infection serotypes. This fever normally affects adults, young children as well as babies with symptoms appearing from 03rd to 14th days after the infective bite. Dengue is not an infectious ailment i.e. transmitted directly from individual to-individual and side effects range from gentle fever to disabling high fever, with serious migraine, pain behind the eyes, muscle and joint pain, and rash. Extreme dengue (otherwise called dengue hemorrhagic fever) is portrayed by fever, stomach pain, constant spewing, draining and breathing trouble and is a conceivably deadly complexity, influencing mostly kids. Once in a while indications are gentle and can be confused for those of this season's flu virus or another viral contamination. More youngsters and individuals who have never had the contamination have a tendency to have milder cases than more seasoned kids and grown-ups. On the other hand, major issues like dengue hemorrhagic fever, an uncommon complication portrayed by high fever, damage to lymph and veins, bleeding from the nose and gums, extension of the liver, and failure of the circulatory framework. The manifestations may advance to excessive bleeding, shock, and death. This is called dengue shock disorder (DSS). Persons having weakened immune framework as well as those with a second or subsequent dengue Page | 109
infection found to be at elevated risk for getting dengue hemorrhagic fever or dengue shock syndrome. Dengue haemorrhagic fever or dengue shock syndrome proceeds through two stages 14. The illness begins with sudden onslaught of fever accompanied by dengue-like symptoms; during or shortly after the fall in body temperature, the condition of the patient suddenly deteriorates, the skin becoming cold, the pulse rapid, and the patient becomes lethargic and uneasy. In some children the range of pulse pressure progressively narrows, the patient becomes hypotensive and if not treated, death may occur within a short duration of 4-6 hours. Ecology of Dengue Fever The causative agent of dengue fever comes under one of five serotypes of the dengue virus (DENV). It is a mosquito-borne, single + stranded RNA infection which falls under the Family- Flaviviridae; Class- Flavivirus (Fig.1.). Each one of the five serotypes can bring about the full range of sickness. The dengue virus (DENV) genome consists 11,000 bases that codes for three basic proteins, layer protein M, capsid protein C, envelope protein E; short non-coding locales on both the 5' and 3' end and seven nonstructural proteins, NS1, NS2a, NS2b, NS3, NS4a, NS4b, NS5.
Fig 1: A TEM micrograph showing dengue virus virions (the cluster of dark dots near the center) (Courtesy: http://wikipedia.org/wiki/File:Dengue.jpg)
Transmission Cycle Dengue virus is primarily transmitted by Aedes mosquitoes, particularly Ae. Aegypti. These mosquitoes typically live between the scopes Page | 110
of 35° north and 35° South beneath a rise of 1,000 meters (3,300 ft) 15. They regularly bite amid the day, especially in the early morning and evening period 15, 16. Different Aedes species that transmit the sickness incorporate Ae. Albopictus, Ae. polynesiensis and Ae. Scutellaris 15. Human are the essential host of the infection17 however it additionally circles in nonhuman primates 18. The infection appears to have no inconvenient impact on the mosquito, which stays contaminated forever 19. Ae. Aegypti is especially included, as it likes to lay its eggs in artificial water compartments, to live in close vicinity to people, and to feed upon individuals instead of different vertebrates. Dengue can likewise be transmitted by means of contaminated blood items and through organ donation 20, 21. Vertical transmission (from mother to child) during pregnancy or at birth has been reported 22. Other man-to-man modes of transmission have also been reported, but are very unusual 23. The genetic variation in dengue viruses is found to be region specific; which suggests that establishment into new areas is relatively infrequent, despite dengue emerging in new regions in recent decades 24. Unplanned developmental of townships plagued with water logging problems accelerated the incidence of vector borne diseases like dengue, chikungunya etc. With regard to dengue vector proliferation, human ecology is directly or indirectly responsible for the creation of a mosquitogenic environment 25. The major tropical vector-borne diseases are usually viewed as environmental price of underdevelopment occurring in communities of developing countries26. Dengue is endemic in India, with reported disease outbreaks in large metropolitan cities 27, 28, 29. The primary report of dengue hemorrhagic fever was recorded in 1963 in Kolkata, which later spread all over India. Delhi, the capital of India experienced a steep emergence of dengue in 1996 with 10,252 cases and 423 deaths 30. There have been outbreaks of this virus in southern India. An estimated population of over 80,000 people in the states of Karnataka and Andhra Pradesh were affected since December 2005 31. Previously unaffected areas disease outbreaks were reported with increased urbanization and population movement 32, 33, 34. Dengue Cases in North Eastern Region of India The North Eastern region of India comprises of eight states, viz. Assam, Arunachal Pradesh, Manipur, Mizoram, Meghalaya, Nagaland, Tripura and Sikkim. DENV activity has been reported from Arunachal Pradesh35 and Nagaland 31 and Assam 35, 36. Various entomological survey carried out in different places of North East India at different seasons reveals the prevalence of potential dengue vectors 37, 38, 39, 40, 41. Various the parts of the Page | 111
North Eastern region of India found positive for the potential vectors of dengue, viz. Aedes aegypti and Ae. Albopictus during extensive entomological surveys carried out in 2004-2005 32. The different breeding habitats with preponderance of Aedes vector was recorded in four different environmental settings (Urban, Industrial, Semi-urban and rural) in all the states of North Eastern region 32. The states of North East India have experienced an increased number of reported fever cases of unknown origin in recent years. The doctors rarely consider dengue as a differential diagnosis of an acute febrile illness. Dengue is an elusive disease with non-specific signs and symptoms, clinical diagnosis of dengue is very critical to ascertain 42, 43 . The prior knowledge of clinical manifestation of dengue and a complete medical history for immediate and timely diagnosis are important for quick supportive medical therapy. Dengue shared some similar symptoms with other infectious diseases prevalent in this region viz. West Nile 44, Chikungunya 36, and Japanese encephalitis 45. Ae. Aegypti and Ae. Albopictus are the main vectors of dengue and are supposedly common in the North-East part of India, which offers perfect natural conditions for multiplication of these mosquito vectors and the spread of illness 32. Serological survey conducted during 1963 in the North Eastern part of India, revealed Dengue activity in the erstwhile greater Darrang district of Assam and Lohit district of Arunachal Pradesh 32, 46. In nineties decade, Dengue (DENV-2) in Nagaland and Assam was also reported 32, 47, 48. During 2009–2011, a study carried out by Dutta et al. (2012) reported 143 laboratory confirmed cases belonging to Assam (82), Meghalaya (35), Nagaland (15), Manipur (8), and AP (3) 49 Dengue cases were reported from Manipur (2007), Nagaland (2009) and parts of Assam such as Silchar and Dibrugarh. All the four dengue virus serotypes (DENV 1, 2, 3 and 4) are active in this region. The serological evidence of dengue virus serotypes 2 and 4 in Assam and Nagaland in 1993 was documented by The Regional Medical Research Centre, Dibrugarh (ICMR). In Assam, around 237 confirmed instances of dengue without precedent for 2010, and thusly there was a critical increment in 2012, 2013 and 2014 with 1058, 4526 and 85 cases recorded, individually 28. The larger parts of cases (70–90%) were recorded in the biggest metropolitan zone, Guwahati city alone. The real disease burden is assessed to be much higher, with numerous cases not properly diagnosed and extra cases reported in government/private segment. The NE region of India particularly the capital of Assam (mainly Guwahati city), has been experiencing DF from July to December every year. Since 2010, DV cases reported from some areas of Page | 112
Guwahati city and other districts. A study carried out by Dutta et al. (2012) reported 143 laboratory confirmed cases belonging to Assam (82), Meghalaya (35), Nagaland (15), Manipur (8), and AP (3). Surveillance of dengue vectors in North Eastern India is important as many cases of dengue are being reported the region 48. A comprehensive picture of dengue epidemic that occurred in Assam state in 2016 enumerated in Table 1 50. In Jorhat districts of Assam, maximum number of cases occurred during the post monsoon season 51. It is also reported that in Uttar Pradesh where the transmission of dengue occurred throughout the year with a peak incidence in the post monsoon period 52. This correlation between outbreak of dengue fever and seasonal variation of disease transmission is very important at local level for institution of effective vector control measures. Dengue transmission occurred equally in rural and urban areas. An increasing number of outbreaks of dengue fever have been reported from rural areas of several southern, northern and western Indian states 52, 53, 54, 55, 56, 57 . Changes in the life style of the rural population as a result of urbanisation as well as water logging in the rainy season, may also be responsible for spread of the disease to rural areas. It was in 2010 that for the first time 237 dengue cases and 2 deaths confirmed to be due to dengue were recorded in Assam state. In the following years except in 2011, there was manifold increase in dengue cases 58. Table 1: District wise distribution of dengue cases in Assam Districts Dengue-positive cases Kamrup 39 Barpeta 2 Sivasagar 2 Nagaon 1 Baksa 4 Dibrugarh 1 Jorhat 1 Hojai 1 Cachar 2 Karbi angling 1 Cachar 2 Nalbari 4 Morigaon 3 Others* 7 *Others mentioned above are those patients who visited to endemic area but residing outside Assam. Page | 113
For each year, of the total confirmed cases, majority (69%-91%) were recorded in Guwahati, the capital city of Assam, during the post-monsoon months in September to December. The district-wise distribution of the cases from the catchment area showed that the present outbreak was mainly concentrated in Jorhat district with a few cases being reported from the adjoining districts. More than 81% of the positive cases were from Jorhat district followed by Sivasagar (6%) and Majuli (5.26%), Golaghat (3.5%) whereas Nagaon, Tinsukia, Dimapur and Guwahati cases were (0.88%)Around 59.6% (n= 68) of the Dengue positive cases resided in urban areas whereas 40.4% (n=46) were from rural areas 51. Table 2: Dengue case details and death since 2010 in Assam Year
Case
Death
2010
237
2
2011
0
0
2012
1058
5
2013
4526
2
2014
27
0
2015
1076
1
2016
6157
4
As per record of National Vector Borne Disease Control Program, Directorate General of Health Services, Ministry of Health and Family Welfare Dengue case details and death since 2010 in Assam (Table 2). Breeding Habitat Aedes species mainly Ae. Aegypti and Ae. Albopictus are the major vectors of arboviral diseases such as dengue, chikungunya, yellow fever etc. Dengue is one of the major and fast emerging tropical mosquito borne diseases. Aedes aegypti and Ae. Albopictus are implicated as disease vectors and breed in a variety of containers. Among these, Ae. Aegypti is a common species in city premises and recorded breeding is predominantly in discarded tyres and solid waste containers. Ae. Albopictus, on the other hand, is commonly encountered in semi-urban/rural areas, breeding in tin/plastic containers, flower vases, cut-bamboo stumps, etc. The spread of Ae. Aegypti, the foremost vector of dengue, in the semi urban zones most likely through public transport is a matter of public health concern. This species was more prevalent in semi-urban areas with close proximity to roads and vehicle garages indicating the probable role of road transport in its geographical spread. Page | 114
According to Khan et al., (2014) Ae. Albopictus was only found in Pasighat hill station, East Siang district of Arunachal Pradesh. The species has been implicated as an efficient potential vector of epidemic Dengue 59, 60. Although it is believed to be a less efficient vector of arboviruses than Ae. Aegypti, the major reported vector of Dengue. However, Ae. Albopictus adapts better than A. aegypti in temperate climate and outbreaks may be caused by this species of mosquitoes in temperate regions and also in areas where A. aegypti is not present 61. But outbreaks caused by A. albopictus are usually smaller and mild in nature. In recent decade, A. albopictus has been the vector in outbreaks in different areas of the world, namely, China 62, Hawaii 63, and Mauritius 64. Control of Dengue Due to unplanned urbanization, high population growth rate and globalization have all been major factors influencing the current pandemic through indirectly providing and creating more larval breeding habitat and consequently increases the mosquito density of that particular areas. As there is no specific vaccine and treatment available for dengue, the vector control only means to reduce the transmission of this disease. It is found that larval density is directly correlated with meteorological and water quality parameters of breeding habitat. Dev et al., (2014) found that the House index was observed rising gradually at the onset of the rainy season and peaked during post-monsoon season 65. A Breteau index lower than 5 denotes a low risk, whereas an index value greater than 50 indicates a high risk of Dengue transmission 66. Knowledge on breeding habitat of Aedes species is vital to provide a better understanding of the interaction between environmental factors. Breeding habitat selection by Aedes mosquitoes is one of the most critical factors for its survival and population dynamics, indirectly causing crucial implications for the control and reduction of dengue transmission. It is essential to know the key components of the ecosystem that will affect the distribution and abundance of mosquitoes. Water quality of the breeding habitat is one of the key component which may affect an oviposition process and the completion of development stages of the Aedes spp. 67, 68. Osmoregulation and oxygen transportation processes in mosquitoes are influenced by pH of water 69. A pH variation outside the range of 7-8, could be used as a tool for management of this vector. Therefore, physico-chemical parameters of breeding habitat of dengue vectors will somewhat assist in the development and intervention for the future mosquito management Page | 115
programs. Ovitrap surveillance is a preferred method for monitoring Aedes mosquitoes due to low material costs, high sensitivity and the ease of management 70. The studies on the potential vectors of dengue in Assam have indicated that Ae. Albopictus is the dominant species in the semi-urban and rural areas 32. The armed forces personnel deployed in North Eastern India are more vulnerable to the incidence of vector borne diseases such as dengue due to their patrolling activities and increased exposure to the environment 71. Till date there is no effective chemotherapy or vaccine is currently available for the prevention or treatment of dengue fever; hence, vector control is the only and the most effective measure currently used to reduce transmission of this deadly disease 72. The importance of seasonal changes in vector density, insecticide susceptibility status of natural populations of the vector species and genetic diversity of vector population are needed in order to formulate the optimum management strategy Knowledge on breeding habitat of Aedes species is vital to provide a better understanding of the interaction between environmental factors. The species composition of the container-breeding mosquitoes and their habitat characteristics need to be studied in the context of the emergence of dengue and chikungunya in this part of the country. The information on the ecological factors influencing mosquito biology such as the physicochemical properties of breeding water could help in better implementation of the vector management programmes 73. The epidemic of dengue transmitted by Ae. Aegypti and Ae. Albopictus are on the rise worldwide, especially in the tropical developing countries 74. In North East India, the first outbreak of dengue reported in Manipur during 2007 and the subsequent increase in the number of cases show the vulnerability of this region to the disease 48. The control measures of this mosquito borne disease are largely dependent on the reduction of vector populations 74. Ovitrap is a rapid, inexpensive and sensitive tool for the monitoring of dengue vectors and is being widely used for mosquito surveillance, spatial distribution studies and for the evaluation of the efficacy of control measures 75. The transmission of mosquito borne diseases is climate sensitive as the mosquitoes need water to breed and ambient temperature is critical to the larval development and the feeding behaviour of adults76. As per the theoretical models, the transmission patterns of dengue are influenced by temperature and precipitation77. Temperature affects the egg viability, larval development, adult longevity and dispersal, whereas rainfall affects the abundance and productivity of the breeding habitats of Aedes mosquitoes 78. The temporal dynamics of Ae. Page | 116
Aegypti populations in San Juan City, Puerto Rico was positively associated with rainfall and temperature 79. Ovitrap surveys in northern Sri Lanka revealed a significant positive correlation between Aedes density and rainfall80. The increase in mosquito density and the number of dengue cases in Manipur, north-eastern India were attributed to the significant changes in rainfall, temperature and relative humidity between 2000-2004 and 20052008 48. A temperature range of 18-33.2°C is considered to be ideal for the transmission of dengue fever and the frequency of feeding increases with temperature 81. The increase in temperature has been found to augment dengue incidence in many countries including Thailand, Indonesia and Mexico 82. According to Das et al., (2014) the analysis of the seasonal pattern of dengue vector density in Sonitpur District of Assam indicated that high densities occur during September-November (post-monsoon), which received 183.1 mm of total rainfall 83. This could be attributed to the availability of breeding habitats such as plant axils, bamboo stumps and discarded coconut shells, which are filled with water after the rains. However, the larval density was relatively low during the monsoon as heavy rains during this period (643.6 mm) were detrimental to the larval breeding in the container habitats. Hence, vector control measures should be intensified after the monsoon rains so as to prevent probable disease outbreaks. The density of dengue vectors was very low during the winter due to low temperature and drying up of the container habitats. 83 The larval density of dengue vectors was used for the estimation of the risk of disease transmission in Sonitpur district. The high risk zone comprised of Dekhiajuli, Behali, Gohpur and Bihaguri PHC, was validated by the dengue incidence data during 2012. The majority (76.9%) of the cases reported during the year were from the high risk zone. The medium risk zone comprising of Balipara and North Jamuguri PHC had 15.4% of the dengue cases, whereas the low risk zone comprising of Biswanath Chariali and Rangapara PHC had 7.69% of the cases 83. In Sonitpur District, all weather parameters studied, including temperature, relative humidity and rainfall were observed to be positively correlated with the dengue vector density. Maximum degree of temperature was having the most significant positive correlation with the Aedes populations, whereas the number of rainy days rather than the total rainfall was more positively correlated with the larval density. Maximum temperature and the number of rainy days accounted for 38.5% variability in dengue vector density in the district 84. Page | 117
Dengue vector surveillance could be improved by Aedes larval sampling methods and by the estimation of the spatial distribution of larvae 85. Surveillance for probable detection of dengue infections, monitoring of vector activity and initiation of vector control measures should be ensured so as to prevent disease transmission in the high risk zones. In the medium and low risk zones, the proliferation of dengue vectors could be prevented by reducing the availability water-holding containers suitable for mosquito breeding. The relationships established between the weather parameters and the abundance of dengue vectors in the study areas could provide valuable inputs for the development of a decision support system for dengue in North Eastern India. Further studies are needed in other parts of the region to understand the seasonal prevalence of Aedes mosquitoes and the factors contributing to their distribution and abundance. However, disease outbreaks depend on factors such as the source of infection, climate and a susceptible human population apart from vector density 76. As dengue cases are being reported from Assam and other parts of North Eastern India, there is a need to identify high risk zones so that future outbreaks could be avoided by targeted interventions. The breeding habitat characteristics were found to exert a significant influence on the abundance of container-breeding mosquitoes in the study areas in Assam, India. The conductivity of breeding water, which was shown to be highly correlated with the larval density, could be used for early warning of the proliferation of disease vectors in an area. However, more studies are needed to validate such relationships in other parts of North Eastern India, before these could be utilised for predicting disease outbreaks. Further, these relationships would also help to enhance the efficacy of the ovitraps used for the monitoring of disease vectors by modifying the physicochemical parameters. Correct identification of the Aedes species involved in arbovirus transmission is very important to design strategies for vector surveillance and control programme. Information of the genetic structure of the Aedes mosquito might add to the advancement of control projects for this vector. Precise vector determination is vital to framework procedures for regulating vector-borne diseases 86. Genetic markers in perspective of the mitochondrial DNA (mt DNA) have been to be profitable for inherited examinations of diverse species and populations 87, 88. Characterization through molecular based tools and Phylogeny related information are lacking from this region India with view to increased Page | 118
mosquito borne diseases. Molecular based data using conserved gene does not identify only to the species and sub species level but they also help in describing the relationship among species and sibling species. North East India is lacking of information related to biogeography, diversity, population genetic structure of this prevailing mosquito species. Proper information in these will decipher the origin, spread and distance wise genetic relations as well as result in correct discriminations. The genetic make-up of this mosquito species by virtue of highly conserved region as North East India needs further focus, exploration and surveillance in this potential vector. Abroviral diseases pose eminent threat to modern civilization; hence vector control is the only prudent and effective mean to break the transmission cycle of the disease until an effective, economical and safe vaccine candidate becomes a reality. A powerful tool in vector control programmes is the application of insecticides. Earlier, the usage of chemical insecticide like DDT (an Organochlorine) was promoted throughout India, which temporarily controlled the widespread outbreak of vector borne diseases like malaria. Poor states like Assam owing to huge burden of vector borne diseases undergone all round unplanned use of insecticides like DDT, permethrin, malathion, deltamethrin, etc. Insects like Culex, Anopheles are smart creatures which quickly develop resistance against insecticides owing to their ill-informed, irrational usage 89. The outbreak of dengue cases warrants the necessity of the study of insecticide resistance in Aedes populations and vector surveillance. This has made dengue becoming one of the most insecticides targeted vectors borne disease 90. The vector control measures with the use of chemical insecticides accelerate the development of insecticide resistance in several dengue vectors including Ae. Albopictus 91. The insecticide resistance mechanism includes the detoxification of insecticides and alteration of insecticide target sites 92. The insects detoxify insecticides by using enzymes, such as cytochrome P450, esterases (α- and β-) or glutathione S-transferases (GSTs) 92 among others GST plays a role in DDT resistance, while non-specific esterase mostly involved in resistance to organophosphates, carbamates and sometime to pyrethroids 93. WHO recommended criteria for characterizing insecticide susceptibility/resistance determines mortality rates greater than 98% after 24 h post exposure as the susceptibility. Wild collected St. albopicta was found to be resistant to DDT and susceptible to malathion, deltamethrin and temephos. High level of knock-down resistance to DDT was also reported94. However, continuous presence of DDT in the environment as result of biomagnification may have attributed to the emergence of resistant vector Page | 119
strains. According to another study which was carried out in NCR Delhi, India where Ae. Aegypti was found to be resistant to dieldrin and DDT, but susceptible to pyrethroid and organophosphates insecticides 95. Singh et al., (2011) had conducted an insecticide susceptibility test in Jharkhand on adult and mosquito larvae, which showed resistance of disease vectors to DDT and susceptibity to other insecticides 96. There are other reports of high levels of DDT and pyrethroid resistance in Ae. Aegypti and Ae. Albopictus in different parts of the world 93, 97, 98. The degree of resistance can easily measure as the proportions of wild adults that have greater enzyme activity levels than those of susceptible lab controls 89. According to Das et al., (2014) that insecticide resistance especially high DDT resistance was observed in all study sites of Sonitpur District, Assam 83. The biochemical study of enzyme systems such as alpha esterase, beta-esterase and GST showed the elevation and the presence of clear correlations between enzyme levels and resistance phenotypes across all study sites. The elevated activity of esterase correlates for resistance to carbamate, organophosphates and pyrethroid type insecticides 99, 100, 101. An increased GST activity can also be correlated with DDT and organophosphates resistance 102, 103, 104. Increased levels high levels of DDT resistance among mosquito populations in the study sites populations may explain the increased level of GST activity. But clear correlation with high esterase activity with pyrethroid resistance cannot be ascertained. Which indicates that high esterase activity may also be contribute to elevated DDT resistance as suggested by Hemingway and Ranson 91. More study task can be taken up to reveal the hidden reasons of Deltamethrin and malathion susceptibility with a high level of esterase activity. Biochemical assays should be used along with conventional bioassays in vector control programmes to improve the surveillance of resistance and monitoring of the efficacy of insecticides. Detection of resistance will help public health personnel to formulate appropriate steps to encounter reductions in effectiveness of control effort that may accompany with the emerging problem of insecticide resistance. Conclusion Moreover early detection and knowledge of the resistance status as well as the underlying mechanisms in vector mosquitoes are essential for effective long term control of dengue vectors. Our study suggests that continuous resistance monitoring should be conducted in the North eastern region to identify the efficacy of compounds for dengue control and to facilitate selection of compounds with the greatest promise for halting or minimising dengue infections. Creating community level awareness, civil Page | 120
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the molecular biology and biochemistry of a major insecticide resistance mechanism. Medical and Veterinary Entomology. 1998; 12(1):1-12. 102. Hemingway J, Malcolm CA, Kisson KE, Boddington RG, Curtis CF, Hill N. The biochemistry of insecticide resistance in Anopheles sacharovi: comparative studies with a range of insecticide susceptible and resistance Anopheles and Culex species. Pesticide Biochemistry and Physiology. 1985; 24:68-76. 103. Penilla PR, Rodrigues AD, Hemingway J, Torres JT, Jimenez JA, Rodrigues MH. Resistance management strategies in malaria vector mosquito control. Baseline data for a large-scale field trial against Anopheles albimanus in Mexico. Medical and Veterinary Entomology. 1998; 12(3):217-223. 104. Chen L, Hall PR, Zhou XE, Ranson H, Hemingway J, Meehan EJ. Structure of an insect delta class Glutathione S- transferase from a DDTresistant strain of malaria vector Anopheles gambiae. Acta Crystallographic a Section D Biological Crystallography. 2003; 59:2211-2217.
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Chapter - 7 Status of Whitefly, Bemisia tabaci as Insect Vector and Their Management: An Overview
Authors Anil Kumar PhD Research Scholar, Department of Entomology, UBKV, Pundibari, Cooch Behar, West Bengal, India Nagend Kumar Jr. Scientist, SRI, Department of Entomology, DRPCAU, Pusa, Samastipur, Bihar, India
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Chapter - 7 Status of whitefly, Bemisia tabaci as Insect Vector and Their Management: An Overview Anil Kumar and Nagend Kumar
Abstract Agriculture crop play a major role in the livelihoods of the rural people. Among major constraints to production worldwide are diseases caused by a group of viruses belonging to the genus Begomovirus, family Geminiviridae. Begomoviruses are plant-infecting viruses, which are transmitted by the whitefly vector (Bemisia tabaci). It is one of the most economically important pests in many tropical and subtropical regions and has been known to cause extreme yield reduction in a number of economically important crops around the world. Several begomoviruses have been detected infecting them in world. Small single stranded circular molecules, alpha satellites and beta satellites, which are about half the size of their helper begomovirus genome, have also been detected in plants infected by begomoviruses. B. tabaci has been associated with suspected begomovirus infections and these are the important pathogens of variety of crops and are responsible for causing huge economic losses. Begomoviruses infecting cotton, chilli, radish, tomato, cassava, sweet potato, pumpkin, papaya etc. Keywords: white fly, insect vector, virus, crops Introduction Over the last 20 years, viruses transmitted by whiteflies have emerged as a global threat to crop production in a wide range of crops. This emergence is due in large part to the movement of plants and plant parts which distribute both vectors and viruses to new locations1 Whitefly and whiteflytransmitted viruses are primarily concerns in dicotyledonous crops. Many of the crops that are adversely affected by these virusesare economically significant and losses occur in both crops for export as well as those critical for subsistence. Many of these viruses are limiting factors in crop production. Some of the greatest losses occur in fiber crops such as cotton; vegetable crops such as cassava, cucurbits, tomato, pepper, common bean, Page | 133
various pulses; agronomic crops such as soybean; and biofuels such as Jatropha. Yield losses, which range from minimal to complete crop failure, depend upon the virus, the crop, the age of the crop at the time of infection, and the incidence of virus-infected plants. Crop resistance to most of these viruses or to feeding by the whitefly vectors has not been developed. In the absence of crop resistance, management of these viruses is usually very challenging, requiring the timely use of numerous management tactics with a heavy reliance on chemicals to limit the feeding, development, and movement of the vector(s) Whiteflies are small, often inconspicuous insects that are globally distributed as agricultural pests of both greenhouse and field crops. Although more than 1,500 species of Whiteflies exist, only a few cause serious economic losses. Their common name, whitefly, is due to the presence of white wax and lipid particles that cover the body and wings of most adult species2. Bemisia. tabaci are polyphagous herbivores that reduce crop yields by extracting water, carbohydrates and amino acids from plant phloem3 and can transmit plant viruses. However, serious viral diseases are more commonly associated with B. tabaci4. As phloem-feeing insects, whiteflies excrete sticky honeydew that can cover fruit and foliage of crops. Honeydew fosters the growth of sooty mold (Cladosporium) on plants and reduces plant photosynthesis3. Whiteflies prefer the undersides of young leaves and have the capacity for rapid reproduction when conditions are favourable. When leaves are disturbed in infested crops, clouds of white flying insects indicate their presence. Whitefly have a wide range of host plants among crops, weed species and ornamental plants. The silver leaf whitefly injects toxic saliva while feeding, causing silvering of leaves in cucurbits and irregular ripening and blotching in tomato fruit. The whitefly is also an important vector or carrier of viruses which result in enormous economic losses in vegetable, grain and fiber crops worldwide. Bemisia tabaci exists as a number of strains or biotypes which are distinguished by host crops, responses to insecticides and DNA ‘fingerprints’. The silver leaf whitefly or B biotype arrived in Australia in the early 1990s. Biotype B is a serious pest in many vegetables including cucurbits, capsicums, tomato, eggplant, brassicae, lettuce, sweet potato and beans. The insect has a high reproduction rate and a short generation time. It also has the ability to quickly develop resistance to insecticides. Classification and Taxonomic Position: Of the more than 1,500 named whitefly species it is thought that this number represents only a small proportion of Aleyrodids in existence5.Most species are found in tropical and Page | 134
subtropical areas. However, some species are known to exist in all major agricultural regions of the world. Based on the diversity of parasitoids in the Pakistan region, researchers have speculated that this is their centre of origin6. Whitefly systematic and classification are complicated because whitefly populations from distinct geographic locations demonstrate considerable variation in host plant preferences, morphology, life histories and even disease-transmission capacities5. For this reason, some whitefly species (i.e. B. tabaci) with distinct populations are further divided into biotypes. Whiteflies, in the order Hemiptera, constitute a single super family, the Aleyrodoidea, within the suborder Sternorrhyncha7. Whiteflies belong to the single family, Aleyrodidae which is most closely related to the Psyllidae in that adults of both groups have two tarsal segments that are almost equal in size5. Aleyrodidae are physiologically unique due to the presence of a vasiform orifice, which is thought to function as a catapult to expel honeydew away from whitefly nymphs. Life History: Hemipterans undergo hemimetabolous development that includes three distinct stages: egg, nymph and imago (adult). Historically, the terms nymph, larvae and pupa have been used to describe whitefly immature. Technically, nymph is the correct terminology but pupa has been widely used to describe the last phase of the fourth instars and will be used here for consistency. Whitefly species classification is based on the last nymphal stage (referred to as the pupa, pupal case, 4th instars, puparium), rather than on the adult stage8. The life cycles of the silver leaf whitefly and greenhouse whitefly are similar, although the two species prefer different temperature ranges for optimal development. The silver leaf whitefly prefers temperatures of 25°C to 30°C for development and rapid generation’ Whitefly eggs are attached to the underside of the leaf surface, usually younger leaves. Eggs hatch in eight to 10 days. There are four immature or nymph stages. Crawlers or first instars nymphs crawl a short distance before settling to feed on plant tissue. Second and third instars nymphs are stationary and remain attached to the leaf surface where they feed until developing into the fourth and final nymphal stage. These fourth instars nymphs stop feeding, pupate and emerge from the pupal case as fully developed adults. The active adult whitefly is largely responsible for virus spread from plant to plant. The silver leaf whitefly takes 18 to 28 days from egg to adult in warm weather and 30 to 48 days in winter. Whitefly-Transmitted Geminiviruses: In plant 47% infection are caused by viruses Geminiviridae family which consists of maximum number of viruses. General symptom of disease caused by geminivirus are curling of Page | 135
leaves, yellowing of veins, yellow mosaic pattern, dwarfing of leaves. Geminiviruses are plant viruses with a circular, single-stranded DNA genome encapsidated in a geminate capsid (pairedicosahedral units) and small plant viruses characterized by a 22 nm ´ 38 nm geminate particle consisting of two joined incomplete icosahedra encapsulating circular singlestranded (ss) DNA genome molecules of about 2700 nucleotides9.The family geminiviridae is divided into four genera mastrevirus, curtovirus, topocuvirus and begomovirus. Begomovirus is one of the biggest genera of the family. It comprise of around 200 species existing worldwide. These economically important whitefly-transmitted viruses are in the family Geminiviridae, genus Begomovirus. The majority of begomoviruses are transmitted by whiteflies in the Bemisia tabaci complex10, which includes Bemisia tabaci (Gennadius) B-biotype. Begomoviruses infect many important agricultural plants worldwide including bean, cassava, cotton, mesta,melon, pepper, potato, squash, tobacco, tomato and watermelon. Status of White Fly Transmitted Viral Diseases on Different Crop Okra Leaf Curl Disease Okra (Abelmoschus esculentus L.) is an important vegetable crop of India and okra leaf curl disease is an emerging serious disease in India. Severe leaf curling symptoms were observed while at the same time some plants showed only yellow vein mosaic in the same field. Severe leaf curling with vein thickening symptom of okra have been observed over the years and posed a serious threat to the Okra cultivation in India. Bhendi yellow vein mosaic virus disease has been reported earlier in India11. Naturally infected plants of Okra develop symptoms like severe leaf curl, vein thickening with stunted plant growth. Recently, associations of betasatellites and alphasatellites causing leaf curling disease in okra have been reported from India12. Pumpkin Yellow Vein Mosaic Virus Pumpkin yellow vein mosaic virus (PYVMV) disease takes a heavy toll infecting the plant at all stages of its growth. It not only inflicts drastic reduction in fruit yield but also severely impairs the fruit size and quality. The causal virus is designated as “Pumpkin yellow vein mosaic virus"(PYVMV) and Ochravina cucurbitae sp. according to Holmes13.The occurrence of this disease was first reported by Vasudeva and Lal14 in Zamindars' fields around Delhi. Later, the disease was reported by Verma15 from New Delhi, Capoor and Ahmad 16 from Pune, Bhargava and Bhargava17 from Uttar Pradesh. Number of whiteflies required for PYVMV transmission the results indicated that though a single whitefly could Page | 136
transmit the virus to an extent of 21.67 per cent, the minimum number of whiteflies required for 100 per cent transmission was fifteen. Earlier, Capoor and Ahmad16 noticed a maximum infection of 77.3 per cent with 20 whiteflies. Subramanian18 reported that 15 whiteflies were required to cause 100 per cent transmission of yellow mosaic virus in Lablab niger. Cohen et al.19 found that five whiteflies caused 100 per cent infection in squash leaf curl virus infected squash plants. Salalrajan20 and Ragupathi 21reported that 15 to 20 whiteflies were required to cause effective transmission of yellow mosaic virus diseases of urdbean and soybean, respectively. However, three whiteflies were sufficient to secure hundred per cent transmission of TLCV on tomato22. Capoor and Ahmad16 reported that even 30 sec. was sufficient for a single whitefly to become viruliferous in the pumpkin plants inoculated with PYVMV. They also found that allowing the insects to feed on disease source for periods longer than 5 min partially inactivated the virus. Tomato Yellow Leaf Curl Virus Tomato yellow leaf curl virus (TYLCV) is a group of whiteflytransmitted geminiviruses that causes extensive damage to tomato crops in many tropical and subtropical regions worldwide23. The genome of TYLCV is either monopartite (Mediterranean isolates) or bipartite (Thailand isolate) 24.While the acquisition and transmission of TYLCV by white flies have been studied in some detail25, the interactions between this geminivirus (as well as others) and Bemisia tabaci are still poorly understood. In a manner similar to that for other whitefly-transmitted geminiviruses26, B. tabaci transmits TYLCV in a persistent, circulative manner25. The virus requires a latent period of 12±24 h in the vector25. The genomic DNA of TYLCV can be detected in B. tabaci individuals 30 min after the beginning of acquisition feeding, and it accumulates in the insects as feeding proceeds27. The virus nucleic acid remains associated with the insects for many days after they have ceased to feed on infected tomato plants 27. Earlier data suggests that at least some geminiviruses are reminiscent of insect pathogens and are deleterious to their whitefly vector. In earlier investigations it was shown that the presence of TYLCV in whiteflies was accompanied by the induction of antiviral factors28. Moreover, it was reported in an abstract that squash leaf curl geminivirus (SqLCV) invaded a number of whitefly organs, tissues and cells and was associated with gross as well as ultrastructural abnormalities of the reproductive, digestive and excretory systems29. In this paper, we present evidence that long-term association of TYLCV with its whitefly vector affects the transmission capacity, longevity and fecundity of the insect.
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Chilli Leaf Curl Disease Chilli is an important commodity that is used as a vegetable, spice, medicinal herb and a source of red pigment. The chilli leaf curl disease (ChiLCD) is a major limiting factor for chilli production in the Indian subcontinent and is invariably caused by begomoviruses30. The symptoms include upward curling of leaves, yellowing and stunted growth of the plant etc. The viruses in this family are divided into seven genera on the basis of the host range, insect vector and genome arrangement31. Interestingly, the symptoms and pattern of tomato leaf curl disease (ToLCD) and ChiLCD are often similar. In India chilli has been reported to be infected with begomoviruses such as ToLCNDV, Chilli leaf curl virus, Tomato leaf curl Joydebpur virus etc.32, which eventually have both monopartite and bipartite genome. An experimental demonstration in 2008 has fulfilled Kochs' postulates for ChiLCD, to be caused by a complex consisting of monopartite chilli leaf curl virus and a betasatellite DNA component33. The full-length genome of begomovirus and its cognate betasatellite DNA component associated with chilli leaf curl disease (ChiLCD) originating from Bijnour, Uttar Pradesh (U.P.), region of India were cloned and sequenced. The pairwise nucleotide sequence identity shared 90%) with Tomato leaf curl Bangladesh betasatellite (ToLCBDB). Mung Bean Yellow Mosaic Disease Mungbean yellow mosaic disease is the most destructive disease in blackgram (Vignamungo (L.) Hepper) which causes severe yield losses. It was first reported in 1960 and now occurs throughout the country. The diseased plants show alternating green and yellow patches. Leaf size is generally not affected, but sometimes the green areas are slightly raised and the leaves show a slight puckering and reduction in size. The leaves become paper white and thin. Mungbean yellow mosaic virus belongs to the genus begomovirus and causes YMD in a number of economically important edible grain legumes including mungbean, urdbean and soybean34. In India, it is grown in almost all States.The virus reported from India is not mechanically transmitted but has been transmitted by the whitefly vector (Bemisia tabaci), not only to several species in the leguminosae but also to Brachiaria ramosa (Gramineae) and Cosmos bipinnatus, Eclipta alba and Xanthium strumarium (Compositae)35. The MYMV causes 85-100 per cent yield loss in the plants that are infected at the seedling stage36.
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Cotton Leaf Curl Disease Cotton is the most important kharif cash crop of north India. Among the various factors responsible for its low production and productivity during the last one and a half decade, cotton leaf curl virus disease (CLCuD) has been found to be one of the major limiting factor. The disease has assumed serious proportions in the most potential irrigated cotton belt of north India comprising an area of around fifteen lakh hectares. The disease caused by a whitefly transmitted Gemini virus was first noticed in Nigeria on Gossypium peruvianum and G. vitifolia37. In India, cotton leaf curl virus disease was first reported on American cotton (G hirsutum) in Sriganganagar area of Rajasthan state during 1993 and during 1994 it appeared in Haryana and Punjab38 states on hirsutum cotton and posed a major threat to its cultivation in northern India39. The disease has appeared in an epidemic form during 1997 in the Rajasthan affecting an area of 0.1 million hactares40. Plants affected by the disease exhibit very unusual symptoms, consisting of vein swelling, upward or downward cupping of the leaves, and the formation of enations on the main veins on the undersides of leaves. Frequently the enations develop into cup-shaped, leaf-like structures which can become as large as the leaf from which they emerge. Unusually CLCuD-affected cotton plants appear greener than non-infected plants due to the proliferation of chloroplast-containing tissues. However, symptoms are variable with cotton variety and, particularly, the age of the plant at infection. Late season infection frequently leads to mild symptoms and little yield reduction. Papaya Leaf Curl Disease In India, leaf curl disease of papaya was first reported by Thomas and Krishnaswamy in 1939. The adverse effect of this disease can be easily observed in papaya growing fields, where most papaya plants are destroyed by this disease41. Furthermore, several reports have suggested that this disease is also widely distributed in other countries, including Pakistan, China, and those in Africa42. In plants, the symptoms that develop following begomovirus infection include downward and upward leaf curling, twisted petioles, venation, and stunting. On the basis of the typical leaf curling symptoms caused by this genus, the resulting disease is termed leaf curl disease. Leaf curl disease of papaya is a begomoviral disease which produces small and distorted fruits that tend to fall prematurely. Because begomoviruses have a high tendency of recombination, they have a wide host range. Management of Whitefly Transmitted Viruses Integrated management methods that reduce or eliminate insecticide use Page | 139
are encouraged for whitefly management as these insects, particularly whitefly, rapidly develop resistance to insecticides, resulting in management crisis. The aim is to maximise cultural and biological controls and minimise insecticide use. Management Methods are Outlined Below Prevent seedling infestation by whitefly and virus infection—use netting or screening and isolation to maximise protection. Do not transport seedling transplants to other farms, districts or regions where whitefly and the viruses are not present. Each virus discussed in this note has a restricted distribution and movement of infested or infected transplants carries a high risk of moving the diseases to new areas. Destroy old and abandoned crops promptly. Ensure that post-harvest destruction of a crop will not result in mass migration of insects to young plantings. Apply an insecticide or oil spray to kill adult whitefly before crop destruction. Control weeds in and around crops and greenhouse areas as these host both whitefly and the viruses they spread. This should occur throughout the year and is critical in the month before planting. Where possible plant new crops upwind from old crops. Plant virus resistant varieties. The level of whitefly management needed to reduce virus infection below economic damage levels is higher than that usually required to manage damage from direct feeding and achieving this will often be a challenge. Resistant varieties are use where these viruses are likely to be a problem. Measures to reduce disease and insect levels should still be used to reduce the chances of resistance-breaking strains developing and overcoming virus resistance. Plastic (polyethylene) soil covers (mulch) are a popular strategy for protection of open-field production against whiteflies and the viruses they transmit (as well as against viruses transmitted by aphids and thrips) 43. Planting seed or vegetatively propagated planting material that is free of viruses provides a crop with the optimal start to its growth cycle. Since whiteflies can fly over distances of several kilometers and they transmit are persistent or semi-persistent26, new crops planted in proximity to older crops that are infested with whiteflies are Page | 140
vulnerable to being infected by viruses present in the neighboring older fields. Patterns of whitefly population increase and decline depend upon several environmental factors, the most important of which are the availability of hosts—determined by the date of planting—and the climatic variables of temperature and precipitation. In general, whiteflies are more abundant during periods of warm weather during which there is active crop growth (resulting from adequate soil moisture) as well as when crop host plants are young and rapidly growing. By careful manipulation of planting dates, therefore, it is often possible to reduce whitefly populations and the resulting incidence of the viruses that they transmit, although this should not be done in a way that makes growing conditions unfavorable for the crop. Traps crops have been shown to be effective in reducing populations of whiteflies, and therefore reducing the level of virus infection. maize either intercropped or rotated with cucumber, tomato, or squash resulted in lower whitefly abundances in the vegetable crops and significantly lower incidences Crop colonization by whiteflies, and the virus transmission that may follow, can be hindered by placing physical barriers between flying whiteflies and the crop host plants that they seek. Permanent protection, usually done by enclosing crop plants in permanent or semi-permanent insect-proof housing, is most appropriate for high value crops that are grown on a relatively small scale. Whitefly populations can be reduced by physically removing these insects from the air space around crop plants in either protected- or open-field situations. The effect is clearly enhanced through the use of an attractant, which is typically the visual cue of the yellow color. Yellow sticky traps, that attract then kill whiteflies, have mainly been used for monitoring populations of the winged adults44. Maximise biological control opportunities. Several parasitic wasps attack whitefly and are valuable management tools. Encarsia species attack both silverleaf whitefly and the greenhouse whitefly with Encarsia formosa being used in integrated pest management programs for Greenhouse whitefly in protected cropping situations. Chemical control, Systemic insecticides applied as seedling Page | 141
drenches or pre-plant soil applications can be effective for whitefly control. Apply insecticides to crops based on insect monitoring. Optimal use of these pesticides requires several considerations. Selection of the insecticide and timing of application are best when applied using the results of field scouts who monitor whitefly populations. Insecticides should be used in a rotation where insecticides with different modes of action are applied so that development of resistance to any one pesticide by the whiteflies is prevented or delayed. Of all the insecticides available the one class that has had the greatest impact on the management of whiteflytransmitted viruses is the neonicotinoids. Unfortunately, the neonicotinoids have been reported to have adverse effects on pollinators. Use registered insecticides targeted to the undersides of leaves and applied with calibrated equipment, small droplet size and high water rates. Select the most appropriate product for the growth stage of the whitefly and crop. Conclusion Insect vector, white fly is a widespread problem where vegetables and fruits are grown as a multi-seasonal crop. Although it can infect a relatively wide range of plant species, It has great impact which limits the production of many tropical and subtropical areas of the world. The primary way the virus is spread short distances is by whitefly B. tabaci species. Over long distance, the virus is primarily spread through the movement of infected plants because it can take up to 3 weeks for disease symptoms to develop, infected symptomless plants could be unknowingly transported. The virus also can be moved long distance by virus-carrying whiteflies that are transported one plant to other plants or via high winds, hurricanes, or tropical storms. Integrated management methods that reduce or eliminate insecticide use are encouraged for whitefly management as these insects, particularly silver leaf whitefly, rapidly develop resistance to insecticides, resulting in management crisis. The aim is to maximize cultural and biological controls and minimize insecticide use. References 1.
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