Productivity of strawberry plants growing under dry and wet conditions ...

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and wet conditions in subtropical Queensland ... of Agriculture and Fisheries, PO Box 5083, Sunshine Coast Mail Center, Nambour, Queensland 4560,. Australia ...
Productivity of strawberry plants growing under dry and wet conditions in subtropical Queensland C.M. Menzel1,a, L.A. Smith1 and J.A. Moisander2 1Department of Agriculture and Fisheries, PO Box 5083, Sunshine Coast Mail Center, Nambour, Queensland 4560, Australia; 2Driscoll’s Australia, 180 Landershute Road, Palmwoods, Queensland 4555, Australia.

Abstract The effect of growing environment on the performance of two strawberry (Fragaria ×ananassa) cultivar/breeding lines (‘Festival’ and ‘Breeding Line 1’) was studied in south-eastern Queensland, Australia. Plants were grown under tunnels or outdoors. Supplementary over-head irrigation was given to the plants outdoors to provide a water supply (irrigation + rainfall) about twice that of the long-term average rainfall for the area. Half the plants under the tunnels or outdoors received the standard sprays to control grey mould, while the other half of the plants received none of these sprays. The yields of the plants in the dry environment under the tunnels (without over-head irrigation) were more than double the yields of the plants in the wet environment outdoors (with over-head irrigation). This result indicates that losses that may occur during a wetter than average season. The plants under the tunnels had lower incidences of rain damage and grey mould than the plants outdoors. There were higher incidences of powdery mildew, and of small and misshaped fruit under the tunnels. Only cultivars with some resistance to powdery mildew should be grown under protected cropping. Spraying reduced the incidence of grey mould outdoors but not under the tunnels. Crops growing under protected cropping in Queensland probably do not need to be sprayed for grey mould. Keywords: Fragaria ×ananassa, plastic high tunnels, protected cropping, climate, fruit disease, yield, cultivars INTRODUCTION Production of strawberries in open field conditions in South-Eastern Queensland is affected by rain most seasons, with rain damage to the fruit, poor pollination, and fruit diseases such as grey mould (caused by Botrytis cinerea) and stem-end rot (caused by Gnomoniopsis fructicola) (Herrington et al., 2013). Earlier studies conducted in Queensland showed that plants growing under high plastic tunnels had up to 40% higher yields than plants growing outdoors (Menzel et al., 2014). These responses were reflected by higher incidences of rain damage and grey mould in the plants growing outdoors. Rainfall during the earlier experiments was slightly lower than the long-term average for the area. Average rainfall (±SE) from May to September in this area over 61 years was 415±29 mm, median rainfall was 375 mm, the lowest rainfall was 59 mm, and the highest rainfall was 1178 mm. Eight out of 61 years have been very dry (500 mm). There have been several reports examining the productivity of strawberry plants growing under plastic tunnels in northern America. Experiments have been conducted in Canada (Medina et al., 2011; Burlakoti et al., 2013), California (Daugovish and Larson, 2009; Larson et al., 2009), Texas (Wallace and Webb, 2013), Kansas (Kadir et al., 2006), and Florida (Salamé -Donoso et al., 2010; Santos, 2013; Santos et al., 2014). The plants growing under the tunnels had higher yields and were protected from frosts, rain, hail and cool or cold growing temperatures. The use of the plastic often extended the production season and reduced the incidence of fruit disease. Xiao et al. (2001) examined the effect of protected cropping on the incidence of fruit a

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Acta Hortic. 1156. ISHS 2017. DOI 10.17660/ActaHortic.2017.1156.132 Proc. VIII International Strawberry Symposium Ed.: Y. Desjardins

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diseases in Florida. The plants were grown under plastic tunnels or outdoors with different fungicide schedules, including no captain or captan every one or two weeks. The mean incidence of grey mould was 88 to 94% lower under the tunnels than outdoors. The incidence of grey mould for the controls under the tunnels was about 1%, and about 7% for plants growing outdoors and sprayed with captan every week. Xu et al. (2000) studied infection of plants with grey mould under plastic tunnels in the United Kingdom. The average level of infection in the fruit in the plants grown under the tunnels was less than 3% over three years. There were no differences in the levels of infection in the control and sprayed plots. It is apparent that the incidence of grey mould can be very low without the use of fungicides under protected cropping. We studied the performance of strawberry plants growing under tunnels and outdoors in South-Eastern Queensland. Supplementary over-head irrigation was given to the plants growing outdoors to provide a water supply (irrigation + rainfall) about twice that of the long-term average rainfall for the area. This was to test the productivity of the plants in a relatively wet season. Half the plants in each group received the standard sprays to control grey mould, while the other half of the plants received none of these sprays. Both groups of plants received the standard sprays used to control pests, and other diseases, including powdery mildew (caused by Podosphaera aphanis). This was to determine whether plants growing under tunnels in Queensland could have a low incidence of grey mould infection without the application of the standard sprays used to control the disease. MATERIALS AND METHODS Bare-rooted transplants of ‘Festival’, and a breeding line noted as ‘Breeding Line 1’ were planted on March 24, 2014 at Palmwoods on the Sunshine Coast in south-eastern Queensland (lat. 26.6°S; long. 152.9°E, elevation 29 m). The plants were grown under plastic high tunnels or in open, outdoor plots as described by Menzel et al. (2014). The plants growing outdoors were watered with over-head irrigation for ten weeks from early July to early September to promote the development of fruit diseases during dry weather. During this time, the total amount of water applied to the crop by the sprinklers was 480 mm or about 7 mm day-1. Half the plants under the tunnels and outdoors received the standard sprays to control grey mould, while the other half of the plants received none of these sprays. Both groups of plants received the standard sprays used to control pests, and other diseases, including powdery mildew (Menzel et al., 2014). The plastic structures used were standard Haygrove tunnels, which are utilized extensively in the United Kingdom and Australia (Haygrove Ltd., Ledbury, UK). The tunnels were 9 m wide and 4 m high. The polythene THP Visqueen luminance plastic was 200 µm thick (BPI Visqueen Horticultural Products, Stevenston, UK) and transmited about 80 to 90% of sunlight. The plants were grown in two tunnels and two outdoor plots (two growing environments). There were two tunnels adjacent to each other and two outdoor plots adjacent to the tunnels. The ‘whole-plots’ (i.e., the tunnel plus outdoor) were randomised in two replicates (as ‘Outdoor 1’, ‘Tunnel 1’, ‘Tunnel 2’, ‘Outdoor 2’). The spray program treatments were applied in split-plots across the whole plots within each replicate. The cultivar/breeding lines were applied in subplots across the split-plots. In the tunnels, the southern end of each tunnel received no direct sunlight from outside, whereas in the northern end of each tunnel, the plots received some direct sunlight in the morning. There was about 3 m of row between the southern and northern blocks in the middle of each tunnel. There was a similar gap between the southern and northern blocks in the outdoor plots. This set-up gave four plots × 40 plants in each plot and 160 plants per treatment. The plastic was placed over the plants at the start of planting, with the sides of the tunnels raised to moderate temperatures close to the plants. Fruit were harvested twice per week for an assessment of marketable yield (fresh weight), total number of fruit/plant and average fruit fresh weight from May to September. Mature fruit were classified as those that were at least 75% coloured. Average seasonal fruit fresh weight is the long-term average value of fruit fresh weight in a treatment pooled across all harvests (marketable fruit). A record was kept of the number of fruit that were affected 896

by rain and/or grey mould or both, or powdery mildew, along with those that were small (less than 12 g fresh weight) and/or misshaped or both, or that had other defects (mainly other disease, surface bronzing or bird damage). Fruit that were affected by rain and grey mould were rated as affected by grey mould. Fruit that were small and misshaped were rated as misshaped. Information was collected on daily minimum and maximum temperatures and relative humidities. There were four Tinytag sensors (Gemini Data Loggers Ltd., Chichester, UK) outdoors and four sensors under the tunnels in each of four plots. The sensors were placed in small weather screens located next to the plants growing along the rows. The sensors were located about 5 cm above the level of the ground. Data were also collected on daily rainfall with a rain gauge. Data on environmental variables, yield, average fruit fresh weight and on defects are presented as treatment means with standard errors (SEs). RESULTS AND DISCUSSION Total rainfall during the harvests from May to September was 285 mm, lower than the long-term average of 415 mm. The over-head irrigation used outdoors from July provided about another 500 mm of water to the canopy. Mean daily maximum and minimum temperatures were similar in the two growing environments (Table 1). Mean daily maximum relative humidities were higher outdoors than under the tunnels, reflecting the use of the over-head irrigation during the day. In contrast, mean daily minimum relative humidities were lower outdoors. These results are similar to those recorded in the previous experiments in Queensland where there were only small differences in temperature and humidity conditions under the tunnels and outdoors (Menzel et al., 2014). The yields of the plants growing in the dry environment under the tunnels were more than 200% the yields of the plants growing in the wet environment outdoors (Table 2). There was no difference in the average productivity of the sprayed and unsprayed plots, while the average yields of the breeding line were higher than the yields of ‘Festival’. Average fruit fresh weight was higher in the plants in the wet environment and in the breeding line. In the earlier experiments, yields under the tunnels were 24 to 38% higher than those outdoors, with rainfall lower than the long-term average for the area (357 and 329 mm versus 415 mm) (Menzel et al., 2014). In these experiments, no over-head irrigation was applied to the plants growing outdoors. Plants growing under tunnels often have higher yields because of protection from frosts, rain, hail and cool or cold growing temperatures (Larson et al., 2009; Santos et al., 2014). The use of the plastic often extends the production season and reduces the incidence of fruit disease (Xiao et al., 2001; Wallace and Webb, 2013). In Queensland, the main benefit of the tunnels is to reduce the losses associated with rain damage and grey mould. The average incidence of fruit defects was about 50% greater in the plants growing in the wet environment outdoors than in the plants growing in the dry environment under the tunnels (Table 3). The total incidence of defects were similar in the two cultivar/breeding lines outdoors, but higher in ‘Festival’ than in the breeding line under the tunnels. About a third to a half of the defects outdoors were due to rain damage and/or grey mould or both. Within this classification, most of the fruit were damaged by rain. The rest of the fruit were mainly culled because they were small and/or misshaped. Within this classification, most of the fruit were small. Differences in the incidence of rain damage and/or mould between the two cultivar/breeding lines were high outdoors, and non-existent under the tunnels. There were relatively high incidences of these defects in the breeding line outdoors. Overall, ‘Festival’ had a higher incidence of small and/or misshaped fruit than the breeding line (Table 3). Losses due to these defects were especially high under the tunnels. The incidence of powdery mildew was very low outdoors, intermediate in ‘Festival’ under the tunnels, and high in the breeding line under the tunnels. The average total incidence of fruit defects was similar in the control and sprayed plots, but with a higher average incidence of grey mould in the control than in the sprayed plots (Table 3). There was a large difference between the incidence of the disease in control and sprayed plots outdoors, and no difference under the tunnels. 897

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Table 1. Average mean daily environmental conditions and ranges in monthly averages in the study with strawberry plants growing in southeastern Queensland. Two cultivar/breeding lines were grown with or without sprays for grey mould under plastic high tunnels or outdoors. The plants growing outdoors were given supplementary overhead irrigation (wet environment), while the plants growing under the tunnels did not (dry environment). Mean Range in Mean daily Range in Mean daily Range in Mean daily Growing daily max. daily max. min. temp. daily min. max. relative daily max. min. relative Range in daily min. environment relative humidity (%) temp. (°C) temp. (°C) (°C) temp. (°C) humidity (%) relative humidity (%) humidity (%) Outdoor 24.2±0.1 22.3-27.0 11.1±0.1 7.9-14.6 99±1 97-100 52±1 43-60 Tunnel 24.3±0.1 22.8-26.7 12.7±0.1 9.3-16.0 84±1 81-87 60±1 55-65 Data are the means (± SEs) of four plots per treatment. Data are the averages from May to September. Max. = maximum; Min. = minimum.

Table 2. Effect of growing environment, spray program and cultivar/breeding line on total marketable yield and average seasonal fruit fresh weight in strawberry plants growing in south-eastern Queensland. The plants were grown under plastic high tunnels or outdoors, and with or without sprays for grey mould. The plants growing outdoors were given supplementary overhead irrigation (wet environment), while the plants growing under the tunnels did not (dry environment). Growing environment, spray program or cultivar/breeding line Yield (g plant-1) Outdoor 349±19 Tunnel 869±37 Control 601±75 Sprayed 617±71 Festival 562±76 Breeding Line 1 656±68 Outdoor control 334±25 Outdoor sprayed 364±29 Tunnel control 869±58 Tunnel sprayed 869±52 Outdoor Festival 291±14 Outdoor Breeding Line 1 408±19 Tunnel Festival 833±61 Tunnel Breeding Line 1 905±45

Avg. fruit fresh wt (g) 25.0±1.1 23.5±1.1 24.1±1.2 24.3±1.0 20.0±0.3 28.4±0.3 24.9±1.8 25.0±1.5 23.4±1.7 23.7±1.5 20.8±0.3 29.2±0.5 19.3±0.3 27.7±0.2

Data are the means (± SEs) of 16 plots per treatment for the growing environment means, means of 8 plots for the cultivar/breeding line means, and means of 4 plots for the growing environment × cultivar/breeding line means.

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Table 3. Effect of growing environment, spray program and cultivar/breeding line on the percentage of fruit with various defects in strawberry plants growing in south-eastern Queensland. The plants were grown under plastic high tunnels or outdoors, and with or without sprays for grey mould. The plants growing outdoors were given supplementary overhead irrigation (wet environment), while the plants growing under the tunnels did not (dry environment). Fruit with Fruit classified Fruit that were Fruit that were Fruit with Fruit with rain damage as affected small and/or classified as powdery mildew some defect and/or mould by mould misshaped misshaped (%) (%) (%) (%) (%) (%) Outdoor 32.2±1.7 14.7±1.1 0.5±0.2 24.9±1.1 7.0±0.7 59.5±1.1 Tunnel 0.6±0.1 0.4±0.1 10.1±1.4 29.5±2.6 5.0±0.3 41.1±1.5 Control 17.9±4.6 8.7±2.2 5.0±1.5 26.8±2.3 5.9±0.5 51.0±3.0 Sprayed 15.0±3.8 6.5±1.7 5.6±1.7 27.6±1.9 6.2±0.7 49.7±2.3 Festival 14.2±3.6 7.0±1.8 2.9±0.6 33.9±1.6 4.6±0.3 52.3±1.9 Breeding Line 1 18.6±4.7 8.1±2.2 7.7±2.0 20.5±0.6 7.5±0.6 48.4±3.3 Outdoor control 35.1±2.5 16.8±1.6 0.5±0.2 24.0±1.7 6.3±0.9 61.4±1.2 Outdoor sprayed 29.4±1.9 12.7±1.0 0.4±0.2 25.7±1.6 7.8±1.0 57.6±1.7 Tunnel control 0.6±0.2 0.5±0.1 9.5±1.9 29.6±4.3 5.5± 0.3 40.6±2.6 Tunnel sprayed 0.5±0.1 0.3±0.1 10.7±2.3 29.4±3.4 4.6±0.5 41.7±1.6 Outdoor Festival 28.0±1.3 13.8±0.2 0.7±0.3 28.6±0.8 4.8±0.4 58.7±1.4 Outdoor Breeding Line 1 36.5±2.4 15.7±2.1 0.2±0.1 21.2±0.9 9.3±0.6 60.4±1.8 Tunnel Festival 0.4±0.1 0.2±0.1 5.1±0.5 39.2±1.4 4.3±0.4 45.8±1.1 Tunnel Breeding Line 1 0.7±0.1 0.6±0.1 15.2±1.1 19.9±0.8 5.7±0.3 36.5±1.4 Growing environment, spray program or cultivar/breeding line

Data are the means (± SEs) of 16 plots per treatment for the growing environment means, means of 8 plots for the cultivar/breeding line means, and means of 4 plots for the growing environment × cultivar/breeding line means. Other defects include mainly other disease, surface bronzing or bird damage, and are not presented.



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The incidence of grey mould is often lower in plants growing under tunnels than in plants growing outdoors (Daugovish and Larson, 2009; Burlakoti et al., 2013). Overall, the incidence of grey mould in these experiments was much lower than the incidence of the disease in Queensland. In Canada, the average incidence of grey mould was 0.2% for plants under the tunnels and 0.8% for plants outdoors. In California, it was 0.7% under the tunnels and 5% outdoors. Half the plots in the current experiment were sprayed with fungicides to control grey mould, while the other plots were left unsprayed. The results of the research suggest that strawberry plants growing under protected cropping in Queensland probably do not need to be sprayed for grey mould, with potential savings in growing costs and the environment. Xiao et al. (2001) showed that the incidence of grey mould in untreated plants growing under tunnels in Florida was less than 2%, and only slightly higher than the incidence in sprayed plants (1%). The development of the powdery mildew fungus is promoted by temperatures between 15 and 25°C and relative humidity above 75% (Kennedy et al., 2013). The conidia are spread by wind, with dispersal inhibited by rain and over-head irrigation. Powdery mildew is significant issue for strawberry production under protected cropping. In Florida, the average incidence of the disease was 6.9% under tunnels and 0.6% outdoors (Xiao et al., 2001). The control of powdery mildew in annual strawberry crops is dependent on the use of resistant cultivars, disease-free transplants and the application of fungicides. Work in Florida showed a range in the resistance of strawberry species and cultivars to the powdery mildew fungus (Kennedy et al., 2013). The higher susceptibility of the breeding line to the disease may make production of this material under protected cropping in Queensland difficult. CONCLUSIONS Strawberry plants under tunnels without supplementary over-head irrigation had lower incidences of rain damage and grey mould than the plants outdoors with supplementary over-head irrigation. There was a higher incidence of powdery mildew under the tunnels, especially in the breeding line, and higher incidence of small and misshaped fruit under the tunnels, especially in ‘Festival’. Only cultivars with some resistance to powdery mildew should be grown under protected cropping. Spraying reduced the incidence of grey mould outdoors. In contrast, the incidence of the disease was very low under the tunnels and not affected by spraying. Strawberry plants under protected cropping in Queensland probably do not need to be sprayed for grey mould. Marketable yields of plants growing under the tunnels were more than double those of plants growing outdoors and given a water application (overhead + rainfall) equivalent to about twice the average rainfall for the area. ACKNOWLEDGEMENTS We thank Horticulture Innovation Australia Limited (HIA Ltd.) and the Florida Strawberry Growers’ Association for supporting this research. The Queensland government has co-funded the research through the Department of Agriculture and Fisheries. Literature cited Burlakoti, R.R., Zandstra, J., and Jackson, K. (2013). Comparison of epidemiology of gray mold, anthracnose fruit rot, and powdery mildew in day-neutral strawberries in field and high-tunnel conditions in Ontario. Int. J. Fruit Sci. 13 (1-2), 19–27 http://dx.doi.org/10.1080/15538362.2012.696956. Daugovish, O., and Larson, K.D. (2009). Strawberry production with protected culture in southern California. Acta Hortic. 842, 163–166 http://dx.doi.org/10.17660/ActaHortic.2009.842.20. Herrington, M.E., Hardner, C., Wegener, M., and Woolcock, L.L. (2013). Rain damage on three strawberry cultivars grown in subtropical Queensland. Int. J. Fruit Sci. 13 (1-2), 52–59 http://dx.doi.org/10.1080/15538362. 2012.696982. Kadir, S., Carey, E., and Ennahli, S. (2006). Influence of high tunnel and field conditions on strawberry growth and development. HortScience 41, 329–335.

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Kennedy, C., Hasing, T.N., Peres, N.A., and Whitaker, V.M. (2013). Evaluation of strawberry species and cultivars for powdery mildew resistance in open-field and high tunnel production systems. HortScience 48, 1125–1129. Larson, K.D., Daugovish, O., and Shaw, D.V. (2009). Optimizing strawberry production and fruit quality with use of protected culture in southern California. Acta Hortic. 842, 171–176 http://dx.doi.org/10.17660/ActaHortic. 2009.842.22. Medina, Y., Gosselin, A., Desjardins, Y., Gauthier, L., Harnois, R., and Khanizadeh, S. (2011). Effect of plastic mulches on yield and fruit quality of strawberry plants grown under high tunnels. Acta Hortic. 893, 1327–1332 http://dx.doi.org/10.17660/ActaHortic.2011.893.156. Menzel, C.M., Smith, L.A., and Moisander, J.A. (2014). The productivity of strawberry plants growing under plastic high tunnels in a wet subtropical environment. Horttechnology 24, 334–342. Salamé -Donoso, T.P., Santos, B.M., Chandler, C.K., and Sargent, S.A. (2010). Effect of high tunnels on the growth, yields, and soluble solids of strawberry cultivars in Florida. Int. J. Fruit Sci. 10 (3), 249–263 http://dx.doi.org/ 10.1080/15538362.2010.510420. Santos, B.M. (2013). Advances on protected culture of berry crops in Florida. J. Am. Pomol. Soc. 67, 11–17. Santos, B.M., Huang, P.W., Salamé -Donoso, T.P., and Whidden, A.J. (2014). Strategies on water management for strawberry establishment and freeze protection in Florida. Acta Hortic. 1049, 509–512 http://dx.doi.org/10. 17660/ActaHortic.2014.1049.75. Wallace, R.W., and Webb, C.J. (2013). Strawberries grown under protected cropping on the Texas high plains. J. Am. Pomol. Soc. 67, 7–10. Xiao, C.L., Chandler, C.K., Price, J.F., Duval, J.R., Mertely, J.C., and Legard, D.E. (2001). Comparison of epidemics of botrytis fruit rot and powdery mildew of strawberry in large plastic tunnel and field production systems. Plant Dis. 85 (8), 901–909 http://dx.doi.org/10.1094/PDIS.2001.85.8.901. Xu, X., Harris, D.C., and Berrie, A.M. (2000). Modeling infection of strawberry flowers by Botrytis cinerea using field data. Phytopathology 90 (12), 1367–1374. PubMed http://dx.doi.org/10.1094/PHYTO.2000.90.12.1367

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