Lepidoptera: Sesiidae - naldc - USDA

ECOLOGY AND BEHAVIOR

Discrimination by Male Dogwood Borer, Synanthedon scitula (Lepidoptera: Sesiidae), Among Traps Baited with Commercially Available Pheromone Lures J. CHRISTOPHER BERGH,1 TRACY C. LESKEY,2

AND

AIJUN ZHANG3

J. Econ. Entomol. 97(2): 344Ð352 (2004)

ABSTRACT The response of male dogwood borer, Synanthedon scitula (Harris) (Lepidoptera: Sesiidae), to four commercially available pheromone lures and to pheromone source concentration was evaluated in Þeld trapping studies in commercial apple orchards in Virginia and West Virginia. Male peachtree borer, Synanthedon exitiosa (Say), lesser peachtree borer, Synanthedon pictipes (Grote & Robinson), and lilac borer, Podosesia syringae (Harris), were also captured in traps baited with all lures tested. Among the lures used, the Scenturion dogwood borer lure was the most attractive to and selective for dogwood borer. Male dogwood borer showed a concentration-dependent response to traps baited with different source concentrations of the pheromone from Scenturion. Chemical analyses revealed that all lures contained principally (Z,Z)-3,13-octadecadien-1-ol acetate (ODDA) but that a signiÞcantly higher percentage of (Z,E) plus (E,Z)-3,13-ODDA was present in the Scenturion lure, compared with the others. Weekly collections of fresh male and female dogwood borer pupal exuviae from April until October in 2002 and 2003 suggested that traps baited with Scenturion lures signiÞcantly underestimated the size of populations in commercial apple orchards. KEY WORDS Synanthedon scitula, Synanthedon exitiosa, Synanthedon pictipes, Podosesia syringae, pheromone

THE DOGWOOD BORER, Synanthedon scitula (Harris) (Lepidoptera: Sesiidae), attacks a broad range of ornamental, fruit, and nuts trees (Engelhardt 1932, Eichlin and Duckworth 1988, Johnson and Lyon 1991) and has become increasingly problematic in apple orchards in northeastern North America (Riedl et al. 1985, Warner and Hay 1985, Weires 1986, Kain and Straub 2001, Bergh and Leskey 2003). The ultimate factor responsible for the increasing pest status of dogwood borer in apple is increased plantings of trees on clonal rootstocks in high-density orchards (Riedl et al. 1985, Kain and Straub 2001). These size-controlling rootstocks promote the formation of adventitious root initials (burr knots) near the base of the tree (Rom 1970, 1973) or on the scion (Marini et al. 2003). Burr knots seem to be desirable oviposition sites for female dogwood borer (Riedl et al. 1985, Warner and Hay 1985, Kain and Straub 2001) and are where infestations of new apple plantings are usually initiated. Commercially available pheromone lures and wing traps are recommended for monitoring dogwood 1 Virginia Polytechnic Institute and State University, Alson H. Smith, Jr. Agricultural Research and Extension Center, Winchester, VA 22602. 2 USDAÐARS Appalachian Fruit Research Station, 45 Wiltshire Rd., Kearneysville, WV 25430. 3 USDAÐARS Plant Science Institute, Chemicals Affecting Insect Behavior Laboratory, BARC-West, 10300 Baltimore Ave., Beltsville, MD 20705-2350.

borer ßight activity in apple orchards (Hogmire 1995). However, there has been much variability and inconsistency surrounding their use in apple and other habitats. Based on work in managed, urban landscapes in Maryland, Davidson et al. (1992) and Braxton and Raupp (1995) concluded that commercially available lures for dogwood borer were not reliable for monitoring adult ßight activity. Using published data from studies conducted in different habitats and geographical regions, Bergh and Leskey (2003) found large variability in the strength of the relationship between the capture of male dogwood borer in pheromonebaited traps and other measures of emergence. Sesiid sex pheromones were Þrst isolated from the congeneric species lesser peachtree borer, Synanthedon pictipes (Grote & Robinson), and peachtree borer, Synanthedon exitiosa (Say), and identiÞed by Tumlinson et al. (1974) as geometrical isomers of 3,13-octadecadien-1-ol acetate (ODDA). Geometrical isomers and corresponding alcohols of 3,13-ODDA are the main components of many sesiid sex pheromones (Tumlinson 1979, Nielsen et al. 1979). In trapping studies, Nielsen et al. (1975) demonstrated that (Z,Z)3,13-ODDA was an attractant for male dogwood borer. Electroantennogram studies revealed that male dogwood borer antennae responded strongly to the (Z,Z) and (E,Z) isomers, less strongly to (Z,E) and least to (E,E) (Nielsen et al. 1979). GreenÞeld (1978) and GreenÞeld and Karandinos (1980) concluded that the

April 2004

BERGH ET AL.: DISCRIMINATION BY MALE DOGWOOD BORER

345

Table 1. Specifications of orchards in which fresh dogwood borer pupal exuviae were collected and/or where traps for capturing male dogwood borer were deployed Orchard

Cultivars

Rootstock

Age

Spacing

Hectares (acres)

Cedar Creek Grade 1, VA Cedar Creek Grade 2, VA Buffalo Marsh Road, VA Arden, WV Kearneysville, WV Inwood, WV

ÔYorkÕ and ÔGolden DeliciousÕ ÔYorkÕ and ÔGolden DeliciousÕ ÔRed CortlandÕ and ÔHoneycrispÕ ÔGalaÕ and ÔGinger GoldÕ ÔGalaÕ, ÔGinger GoldÕ ÔGinger GoldÕ

M.26 M.26 M.7 and M.111 M.26 M.26 M.26

3 yr 3 yr 2 yr 7 yr 5 yr 6 yr

7Õ ⫻ 16Õ 7Õ ⫻ 16Õ 16Õ ⫻ 24Õ 10Õ ⫻ 20Õ 10Õ ⫻ 19Õ 10Õ ⫻ 18Õ

0.66 (1.62) 1.96 (4.86) 1.96 (4.86) 1.54 (3.80) 0.89 (2.20) ⬎80 (⬎200)

(E,Z) isomer inhibited the response of male dogwood borer to (Z,Z) and that dogwood borer was at least partially reproductively isolated from some sympatric species of Sesiidae because of this antagonism. Other Þeld trapping studies seem to have conÞrmed the inhibitory effect of small amounts of (E,Z) on the capture of male dogwood borer (Karandinos et al. 1977, GreenÞeld 1978, Warner and Hay 1985), although Snow et al. (1985) suggested that a 96:4 (Z,Z): (E,Z) blend and 99% pure (Z,Z) captured equivalent numbers of moths. The (E,E) isomer has not been considered a behaviorally active compound for dogwood borer, whereas the role of (Z,E) remains unclear. GreenÞeld (1978) concluded that the (E,E) and (Z,E) isomers neither synergized nor inhibited the response of male dogwood borer to (Z,Z), although more males were captured in 1975, 1976, and 1977 in traps baited with a blend of (Z,Z) and (Z,E) than with (Z,Z) alone. Karandinos et al. (1977) reported that a (Z,Z):(Z,E) blend did not enhance the capture of moths, relative to the number responding to (Z,Z). Studies on the seasonal ßight activity of another sesiid, grape root borer, Vitacea polistiformis (Harris), revealed another blend of compounds to which dogwood borer males respond. Traps baited with grape root borer sex pheromone, a 99:1 blend of (E,Z)-2,13ODDA and (Z,Z)-3,13-ODDA (Snow et al. 1987), caught relatively small numbers of male dogwood borer in nine of 13 states, but 597 moths were trapped in South Carolina (Snow et al. 1991). Alm et al. (1989) also reported capturing dogwood borer in traps baited with grape root borer pheromone in Ohio. At present, there are two pheromones listed for dogwood borer on Pherolist (Anonymous 2003a), (Z,Z)-3,13-ODDA and 99:1 (E,Z)-2,13:(Z,Z)-3,13-ODDA. Regardless of the different results reported from Þeld studies in which dogwood borer has been captured in traps baited with different compounds and blends of compounds, recent studies have relied on commercial lures presumably containing primarily (Z,Z)-3,13-ODDA (Pfeiffer and Killian 1999) or lures known to contain the pure compound (Eliason and Potter 2000). Lures containing pure (Z,Z)-3,13-ODDA or those marketed for capturing particular species of clearwing moths, including dogwood borer, are often not species speciÞc, attracting males of nontarget, sympatric species, or genera of Sesiidae (Rogers and Grant 1990, Braxton and Raupp 1995, Pfeiffer and Killian 1999). Furthermore, several studies have reported differ-

ences in the relative attractiveness of commercially available pheromone lures to dogwood borer. Riedl et al. (1985) reported greater effectiveness of the Scentry clearwing borer microÞber lure (Scentry Inc., Billings, MT) than of rubber septa, peachtree borer lures from Pherocon (Tre´ ce´ Inc., Salinas, CA). Braxton and Raupp (1995) suggested that more dogwood borer were captured in Maryland by the Tre´ ce´ lilac/ash borer lure than by the Scentry dogwood borer lure. Pfeiffer and Killian (1999) reported that the Tre´ ce´ lilac borer lure captured signiÞcantly more male dogwood borer than the Tre´ ce´ dogwood borer lure in Virginia, and this observation was independently conÞrmed in West Virginia in 2000 (H. W. Hogmire, personal communication). Bergh and Leskey (2002) captured more dogwood borer with Scenturion dogwood borer lures (Scenturion Inc., Clinton, WA) than with Tre´ ce´ lilac borer lures in Virginia apple orchards, but found that differences between the Tre´ ce´ lilac borer and dogwood borer lures were inconsistent between two orchards in West Virginia. The poor selectivity of pheromone lures for trapping some clearwing moths and the discrepant reports regarding their effectiveness for capturing dogwood borer highlight the need for reÞnement and standardization of a pheromone based monitoring system for this species. The objectives of this research were to compare several commercially available pheromone lures for their attractiveness to and selectivity for dogwood borer. The chemical composition of the lures tested was measured and compared. Pheromone from the most effective lure was used to determine the optimal pheromone concentration for trapping dogwood borer in apple. The accuracy with which the most effective lure reßected the abundance of dogwood borer was examined by comparing the capture of males in traps with the abundance of male and female pupal exuviae. Materials and Methods Test Orchards. Three orchards in Virginia and three in West Virginia were used. Horticultural details of the orchards are presented in Table 1. All orchards were managed for disease and other arthropod pests according to standard practices followed in the midAtlantic region (Anonymous 2003b). The orchards at Cedar Creek Grade 1 and 2, Buffalo Marsh Road, Inwood, and at Kearneysville were not treated with pesticides speciÞcally for dogwood borer. In the Ar-

346

JOURNAL OF ECONOMIC ENTOMOLOGY

den West Virginia orchard, a trunk drench spray of chlorpyrifos was applied in mid June to trees in all rows except the six rows used in this study. Lure Comparison. Lures obtained from commercial suppliers included the Scenturion dogwood borer lure (Scenturion Inc., now available from Suterra LLC, Bend, OR), the Tre´ ce´ lilac borer and dogwood borer lures (Tre´ ce´ Inc.), and the Scentry dogwood borer lure (Scentry Biologicals). The Scenturion and Tre´ ce´ lures were formulated as red rubber septa, whereas the Scentry product was a microÞber lure. Lures were deployed in Pherocon 1C (Tre´ ce´ Inc.) traps, including blank control traps, placed in trees at ⬇1.22 m (4 feet) above the ground (Riedl et al. 1985, Hogmire 1995), and replicated three times per orchard. At the Cedar Creek Grade orchards 1 and 2 and at Buffalo Marsh Road, lures were randomized within each of three rows separated by three buffer rows, and traps were spaced at 21.3-m (70-foot) intervals within a row. Traps remained in their original locations for the duration of each trial. At the Arden and Kearneysville orchards, lures were also randomized within each of three rows separated by one buffer row, and traps were spaced at ⬇24.4-m (80-foot) intervals within a row. Traps were rotated among positions within each row at weekly intervals for the duration of each test. The number of male dogwood borer; lilac borer, Podosesia syringae (Harris); peachtree borer; and lesser peachtree borer captured was recorded weekly for periods ranging from 3 to 6 wk among orchards. Depending on the orchard, trapping periods spanned late May or mid-June through mid-July, early August through mid-September or late August through late September. The number of peachtree and lesser peachtree borers captured were pooled (peachtree borers comprised nearly all captures in this category). The total number of each species captured per trap during the trial was compared among lures for each orchard using PROC GLM of SAS (SAS Institute 1988) and TukeyÕs honestly signiÞcant difference (HSD) at the 5% probability level. Concentration Response. Red rubber septa lures containing different loadings of the attractant used in the Scenturion dogwood borer lures were supplied by the manufacturer (Scenturion Inc.). The 1⫻ loading was equivalent to 1 mg per lure. In the Þrst repetition of this trial, lures with 0.01⫻, 0.10⫻, 0.5⫻, and 1⫻ and blank controls were tested. In the second repetition, a 2⫻ loading (two by 1⫻ lures) was added to the array. All lure loadings were replicated three times per orchard using Pherocon 1C traps, with the exception of the Cedar Creek Grade 1 orchard, in which Pherocon IIID (Tre´ ce´ Inc.) traps were used. Trap/lure deployment at the different orchards was the same as described previously, and all traps were checked weekly, for 3Ð7 wk, for the capture of dogwood borer and other clearwing moths. For each location, source concentration was used as the independent variable and regressed against weekly trap captures of dogwood borer, peachtree and lesser peachtree borers, and lilac borer to determine the concentrationÐresponse rela-

Vol. 97, no. 2

tionship using a linear regression model (SAS Institute 1988). Lure Extractions. Gas chromatography (GC) analyses of pheromone lures were performed on a HewlettÐPackard 6890 gas chromatograph equipped with a DB-WAXETR capillary column (J&W ScientiÞc Inc., Folsom, CA, 60 m by 0.25-mm i.d., 0.25-␮m Þlm-thickness, 120⬚C for 2 min, and then programmed to 250⬚C at 10⬚C/min and held for 10 min) or a DB-5 capillary column (60 m by 0.25-mm i.d., 0.25-␮m Þlm-thickness, 50⬚C for 2 min, and then programmed to 300⬚C at 15⬚C/min and held for 50 min) in the splitless mode with hydrogen as carrier (1.4 ml/min). The ßame ionization output signals were recorded using HewlettÐPackard ChemStation software. Electronic impact GCÐmass spectrometry (GCMS) analyses of pheromone lures were conducted on a HewlettÐPackard 6890 GC coupled to a HP 5973 mass selective detector using an identical DB-WAXETR capillary column (120⬚C for 2 min and then programmed to 230⬚C at 15⬚C/min and held for 15 min) but with helium as carrier gas. A 70-eV electron beam was used for sample ionization. The ion, m/z 248, was selected as the monitor ion. Five pheromone lures from each commercial supplier (Scenturion DWB, lot #16521714 and 20021714; Scentry DWB, lot #LDB 2038102; Tre´ ce´ DWB, lot #32041341; and Tre´ ce´ LB, lot #31630881) were placed individually into 3 ml of hexane in a 4-ml vial and soaked for 3 h. Five Scenturion lures (lot #20021714) deployed in apple orchards in Kearneysville, WV, from 23 July until 27 August 2003 also were analyzed. Extracts (20 ␮l each) were diluted with hexane to an approximate volume (⬇10 ng/␮l) for GC and GCÐMS analyses. Data on the percentage of (Z,E) plus (E,Z)-3,13-ODDA were square-root transformed (公␹ ⫹ 0.5) to normalize the variance before analysis. Means were compared by one-way analysis of variance (ANOVA) followed by RyanÐ EinotÐGabrielÐWelsch range test (SPSS 10.0 for Windows, SPSS Science, Chicago, IL) for signiÞcance at ␣ ⫽ 0.05. Trap Catch versus Abundance of Pupal Exuviae. In April 2002 and 2003, two commercial apple orchards that showed evidence of infestation by dogwood borer were selected. In 2002 and 2003, respectively, 30 and 25 trees with fresh frass on burr knot tissue below the graft union were ßagged and numbered in each orchard. Pupal exuvia remaining on the burr knots from the previous season were removed from the trees at Þrst inspection. At weekly intervals thereafter, all fresh pupal exuviae found below the graft union on each tree were collected and sexed according to the number of rows of posteriorly projecting spines on the fused, terminal abdominal segments (Leskey and Bergh 2003). Beginning in late April or early May, two Pherocon 1C traps baited with Scenturion dogwood borer lures were deployed at a height of 1.22 m (4 feet) in trees in each orchard and placed in different parts of each planting. Traps were monitored weekly through mid-October for dogwood borer males, on the same days that pupal exuviae were collected. A comparison of the cumulative number of males in traps and

April 2004 Table 2.


347

Capture of male dogwood borer and other clearwing moths in traps baited with different commercial pheromone lures, 2002

Lure

Scenturion dogwood borer Scentry dogwood borer Tre´ ce´ dogwood borer Tre´ ce´ lilac borer Blank

Meana ⫾ SD no. moths captured per trap (3 traps/lure) Dogwood borer

Peachtreeb borers

Lilac borer

Cedar Creek Grade 1, VA (28 MayÐ9 July) 3.0 ⫾ 2.6a 4.7 ⫾ 3.1a 6.7 ⫾ 2.3ab 0.7 ⫾ 0.6a 39.3 ⫾ 2.1c 12.0 ⫾ 8.0a 0.0a 17.3 ⫾ 8.4b 4.0 ⫾ 4.4ab 0.7 ⫾ 0.6a 9.3 ⫾ 1.5ab 2.0 ⫾ 0.0ab 0.0a 0.0a 0.0b


Buffalo Marsh Road, VA (7 Aug.Ð18 Sept.) 16.3 ⫾ 14.7a 2.0 ⫾ 1.7a 0.7 ⫾ 0.6a 12.3 ⫾ 10.1a 13.7 ⫾ 2.3c 1.0 ⫾ 1.0a 1.7 ⫾ 1.5a 1.0 ⫾ 1.0a 0.7 ⫾ 1.2a 2.0 ⫾ 1.0a 9.0 ⫾ 1.0b 0.0a 0.0a 0.0a 0.0a


Kearneysville, WV (21 Aug.Ð25 Sept.) 16.7 ⫾ 10.1a 3.7 ⫾ 2.5a 0.0a 1.7 ⫾ 0.6b 72.0 ⫾ 27.5b 0.0a 0.7 ⫾ 0.6b 14.0 ⫾ 15.1a 0.0a 0.3 ⫾ 0.6b 17.7 ⫾ 6.7a 0.3 ⫾ 0.6a 0.0b 0.0a 0.0a

Dogwood borer

Peachtree borers

Lilac borer

Cedar Creek Grade 2, VA (18 JuneÐ9 July) 18.7 ⫾ 10.1a 3.7 ⫾ 3.1a 0.3 ⫾ 0.6a 3.3 ⫾ 3.5b 34.0 ⫾ 12.2b 3.0 ⫾ 2.6a 1.3 ⫾ 1.5b 12.3 ⫾ 2.5a 0.7 ⫾ 1.2a 2.0 ⫾ 2.6b 9.0 ⫾ 6.9a 0.0a 0.0b 0.0a 0.0a Arden, WV (29 MayÐ9 July) 52.7 ⫾ 7.2a 4.3 ⫾ 0.6ab 12.3 ⫾ 4.2b 25.3 ⫾ 8.1c 8.7 ⫾ 5.1bc 10.0 ⫾ 4.4abc 7.7 ⫾ 2.3bc 18.0 ⫾ 11.4bc 0.0c 0.0a

4.0 ⫾ 3.6a 7.0 ⫾ 5.6a 2.3 ⫾ 1.2a 2.0 ⫾ 1.0a 0.0a

a Means within columns for each orchard location followed by the same letter are not signiÞcantly different according to TukeyÕs HSD test at the 5% probability level. b Represents mean number of peachtree and lesser peachtree borers.

the cumulative number of male and female pupal exuviae collected was used to examine the ability of traps to reßect the abundance of dogwood borer. Results Lure Comparison. The Scenturion dogwood borer lure captured more male dogwood borer than the others at all Þve orchards (Table 2) and signiÞcantly more at three locations; Cedar Creek Grade 2 (F0.05, 4,10 ⫽ 7.17; P ⬍ 0.01), Arden (F0.05, 4,10 ⫽ 64.27; P ⬍ 0.0001), and Kearneysville (F0.05, 4, 10 ⫽ 7.49; P ⬍ 0.01). The Scentry dogwood borer lure captured the greatest number of peachtree and lesser peachtree borer males at all Þve sites and signiÞcantly more than the other lures at four orchards; Cedar Creek Grade 1 (F0.05, 4,10 ⫽ 41.60; P ⬍ 0.0001), Cedar Creek Grade 2 (F0.05, 4,10 ⫽ 12.51; P ⬍ 0.001), Buffalo Marsh Road (F0.05, 4,10 ⫽ 51.18; P ⬍ 0.0001), and Kearneysville (F0.05, 4,10 ⫽ 12.32; P ⬍ 0.001) (Table 2). The Scentry dogwood borer lure also captured the greatest number of lilac borer at four orchards (only a single male lilac borer was captured at the Kearneysville orchard), although differences among the lures were not signiÞcant (Table 2). The Tre´ ce´ dogwood borer and lilac borer lures captured numerically more peachtree and lesser peachtree borers than the Scenturion dogwood borer lure at four orchards. A qualitative evaluation of the effectiveness of the lures, based on pooled data among the Þve locations, shows the following rank orders for 1) dogwood borer, 2) peachtree and lesser peachtree borers, and 3) lilac borer, respectively (lures indicated as being equal had pooled totals differing by ⱕ10 moths): 1) Scenturion dogwood borer ⬎ Scentry dogwood borer ⬎ Tre´ ce´ dogwood borer ⫽ Tre´ ce´ lilac borer; 2) Scentry dogwood borer ⬎ Tre´ ce´ lilac

borer ⬎ Tre´ ce´ dogwood borer ⬎ Scenturion dogwood borer; and 3) Scentry dogwood borer ⬎ Scenturion dogwood borer ⬎ Tre´ ce´ dogwood borer ⫽ Tre´ ce´ lilac borer. Concentration Response. Lures containing from 0 to 1.0⫻ and 0 Ð2.0⫻ loadings of the Scenturion dogwood borer formulation produced a signiÞcant linear relationship between source concentration and catch of dogwood borer males at all four locations, of peach borer males at three of four locations, and of lilac borer at one of four locations (Table 3; Fig. 1A and B). The lack of a relationship for lilac borer at three locations and for peachtree and lesser peachtree borers at one location was due to low numbers of moths captured (Table 3). Pheromone source concentration explained between 55 and 89% of the variability for dogwood borer (Fig. 1A) and from 52 to 77% for peachtree and lesser peachtree borers (Fig. 1B). Lure Extractions. Although the GC proÞles varied among the different commercial lures, chemical analyses indicated that all lures contained (Z,Z)-3,13ODDA as the major component, and (Z,E)- and (E,Z)-3,13-ODDA as minor components (Fig. 2). This result was conÞrmed by comparison of mass spectra, GC retention times, and coinjection on both polar and nonpolar capillary columns with synthetic standards (Bedoukian Research, Danbury, CT, and Pherobank, Wageningen, The Netherlands). The greatest percentage of the (Z,E) plus (E,Z) isomers was found in the Scenturion dogwood borer lure, followed by the Tre´ ce´ dogwood borer, Tre´ ce´ lilac borer, and Scentry dogwood borer lures. A signiÞcantly higher percentage of the (Z,E) plus (E,Z) isomers was found in the Scenturion lure compared with other lures (F0.05,4,20 ⫽ 79.99; P ⬍ 0.0001). The percentage of minor components in Scenturion lures did not change after

348


Vol. 97, no. 2

Table 3. Outcome of linear regression analyses of the relationship between pheromone source concentration and the number of male dogwood borer, peachtree/lesser peachtree borer and lilac borer captured in pheromone traps at four commercial apple orchards in Virginia and West Virginia, 2002 Peachtree borersb

Dogwood borer Orchard

Sample datesa

No. monthsc

F

Cedar Creek Grade 1, VA Cedar Creek Grade 2, VA Arden, WV Kearneysville, WV

18 JuneÐ9 July 14 Aug.Ð18 Sept. 28 MayÐ9 July 21 Aug.Ð1 Oct.

113 111 471 178

15.87 29.71 108.33 23.95

P

No. months

F

0.002 0.001 0.0001 0.0002

1 131 59 136

0.20 33.78 44.18 17.61

Lilac borer P

No. months

F

P

0.66 0.0001 0.0001 0.0007

0 1 6 8

NA 0.30 4.11 12.85

NA 0.594 0.064 0.003

NA, not applicable. Pheromone source concentration ranged from 0 to 1.0⫻ at Cedar Creek Grade 1 and Arden orchards and from 0 to 2⫻ at Cedar Creek Grade 2 and Kearneysville. b Represents number of peachtree and lesser peachtree borers. c Pherocon 1C traps used except at Cedar Creek Grade 1, where Pherocon IIID traps were used. a

deployment in the Þeld for 5 wk (Fig. 3, ScenturionF). Trap Catch versus Abundance of Pupal Exuviae. Traps baited with the Scenturion lure reßected the onset of emergence of the overwintering population

of dogwood borer (Fig. 3AÐD). The Þrst male moths were captured and the Þrst male pupal exuviae were collected on the same date at two sites (Fig. 3B and C). At one site (Fig. 3A), male exuviae were Þrst collected 1 wk before the capture of the Þrst moths, and at another (Fig. 3D), male moths were captured 2 wk before Þnding the Þrst male pupal exuviae. Cumulative counts of the number of male and female pupal exuviae tracked one another closely at the four orchards, and based on the total number of exuviae of each gender collected over the season, a 1:1 sex ratio was indicated (Fig. 3AÐD). Among the four orchards, the total number of male moths captured and the total number of male pupal exuviae collected from May until October averaged 104.8 ⫾ 74.2 and 45.8 ⫾ 18.8 SD, respectively. Discussion

Fig. 1. Relationship between pheromone source concentration and capture of (A) male dogwood borer at four commercial apple orchards in Virginia and West Virginia, 2002; and (B) capture of male peachtree and lesser peachtree borer at three commercial apple orchards in Virginia and West Virginia, 2002. CoefÞcients of determination (r2) for dogwood borer at Cedar Creek Grade 1, Arden, Cedar Creek Grade 2, and Kearneysville were 0.55, 0.89, 0.65, and 0.60, respectively. CoefÞcients of determination for peachtree and lesser peachtree borer at Arden, Cedar Creek Grade 2 and Kearneysville were 0.77, 0.68, and 0.52, respectively.

Our comparison of pheromone lures indicated that dogwood borer males discriminated among the stimulus sources offered. The greater attractiveness of the Scenturion dogwood borer lure concurs with our earlier, albeit less extensive, comparison (Bergh and Leskey 2002). Differences among these lures may be due primarily to variation in isomeric content. Chemical analyses of each lure type revealed that all lures contained principally (Z,Z)-3,13-ODDA, but that the Scenturion product contained a greater percentage of (Z,E) plus (E,Z)-3,13-ODDA than the others (Fig. 2). Measurements of the ratios of the (Z,Z) and (Z,E) plus (E,Z) isomers of ODDA formulated in the lures deployed in our studies revealed that the Scenturion, Tre´ ce´ dogwood borer Tre´ ce´ lilac borer, and Scentry lures contained 94.3:5.7, 95.6:4.4, 98.5:1.5, and 99.1:0.9% (Z,Z):(Z,E) plus (E,Z), respectively. In electrophysiological studies, dogwood borer antennae responded strongly to (Z,Z)- and (E,Z)-3,13ODDA, although the (Z,E) isomer also elicited a response that, in magnitude, was ⬇28% of the response to (Z,Z) (Nielsen et al. 1979). The strong response to the (E,Z) isomer is likely associated with the reproductive isolation of S. scitula from sympatric species of Sesiidae (GreenÞeld 1978). Trapping studies have re-

April 2004


349

Fig. 2. Mean (⫾SE) percentage of (Z,E) plus (E,Z)-3,13-ODDA present in Scenturion dogwood borer, Scentry dogwood borer, and Tre´ ce´ lilac and dogwood borer lures. Scenturion-F, ÞeldÐaged lure. Means followed by the different letters are signiÞcantly different at ␣ ⫽ 0.05 (one-way ANOVA, square-root transformed, RyanÐEinotÐGabrielÐWelsch range test, n ⫽ 5, F4,20 ⫽ 79.99, P ⬍ 0.001).

peatedly documented that the addition of a small amount of the (E,Z) isomer inhibits the response of male dogwood borer to (Z,Z) (Karandinos et al. 1977, GreenÞeld and Karandinos 1979, Warner and Hay 1985), although data in conßict with that observation have also been reported (Snow et al. 1985). Although GreenÞeld (1978) concluded that neither the (E,E) nor the (Z,E) isomers synergized the response of dogwood borer males to (Z,Z), his data do show instances of greater numbers of males being captured in traps baited with a combination of (Z,Z) and (Z,E) than with (Z,Z) alone. Differences in the loading or release rate among products could have inßuenced our results and cannot be disregarded, although we assume a standard pheromone loading rate of 1 mg per lure. Because information about product formulation is proprietary, we can only speculate about the inßuence of those potential factors. The results of our trapping studies clearly indicate pronounced and consistent differences among the lures tested. Chemical analyses of these lures also revealed differences among them. It is not our intention to draw conclusions about the effect(s) of the (E,Z) or (Z,E) isomers on our results. Rather, we present these data because of the differences found and to stimulate continued examination of the chemical ecology of dogwood borer and other sesiid pests, toward improved monitoring and management capabilities. Selectivity of commercially available lures is important to optimizing their effectiveness as monitoring tools. InterspeciÞc or intergeneric attraction to isomers of 3,13-ODDA has been commonly reported for many sesiid species (Nielsen et al. 1975, Snow et al.

1985, Rogers and Grant 1990, Meyer and Cranshaw 1994, Braxton and Raupp 1995, Pfeiffer and Killian 1999). In a summary of the pheromones used by species of clearwing moths found in the north central United States, Taft et al. (1991) stated that the information should be used only as a general guide, because moths may be attracted to several chemicals or blends of compounds. In our tests, the Scenturion lure was the most selective for dogwood borer, capturing fewer peachtree and lesser peachtree borers and lilac borers than the other lures. The Scentry lure was most attractive to peachtree and lesser peachtree borers, most of which were peachtree borer. Previous trapping experiments have shown that peachtree borer responds optimally to blends (93:7Ð98:2) of (Z,Z): (E,Z)-3,13-ODDA (Nielsen et al. 1975, Barry et al. 1978), whereas lesser peachtree borer is most attracted to the pure (E,Z) isomer (Tumlinson 1979). Using the attractant formulated in the Scenturion dogwood borer lure, we demonstrated a signiÞcant pheromone source concentration-dependent response by male dogwood borer at all four sites and by peachtree and lesser peachtree borers at three locations (Table 3). Pheromone source concentration explained from 52 to 89% of the variability in the capture of male moths (Fig. 1A and B). The similar concentration-dependent responses of dogwood borer and the peach borers to the attractant in the Scenturion lures suggests that the greater selectivity for dogwood borer and the peachtree and lesser peachtree borers elicited by the Scenturion and Scentry lures, respectively, may have been due more to the ratios of the (Z,Z) and (Z,E) plus (E,Z) isomers than to the source concentration of pheromone.

350


Vol. 97, no. 2

Fig. 3. Cumulative capture of male dogwood borer in traps baited with Scenturion dogwood borer lures (n ⫽ 2 traps/orchard) and cumulative number of fresh male and female dogwood borer pupal exuviae collected from burr knots on trees in commercial apple orchards. Pupal exuviae were collected from 30 trees per orchard at (A) Cedar Creek Grade 2, Winchester, VA, 2002, and (B) Buffalo Marsh Road, Winchester, VA, 2002; and 25 trees per orchard at (C) Cedar Creek Grade 2, Winchester, VA, 2003, and (D) Inwood, WV, 2003.

Although commercially available pheromone lures and wing traps are recommended for monitoring dogwood borer in apple orchards (Hogmire 1995), the relationships between the number of males captured in traps, larval density, or horticultural impact(s) on infested trees remain unknown. The presence of adults and peak emergence periods can be determined, although traps baited with the Scenturion lure may not have accurately reßected the size of resident dogwood borer populations in apple orchards. Given that the number of male moths available for capture in an orchard can be extrapolated from the abundance of male pupal exuviae collected, we would expect higher trap counts than what we recorded, if the lures were optimally attractive. In 2002 and 2003, pupal exuviae were collected from just 30 and 25 trees per orchard, respectively, in infested orchards that were comprised of ⬇1000 to many thousands of trees. Yet, among the four orchards, the average total number of male moths captured over the season was not much greater than the average total number of male pupal exuviae found. This Þnding suggests that even the most attractive lure may not have competed well with calling virgin female moths in the orchards, an inference that is supported by our observations of the response of males to traps baited with caged, virgin females compared with those containing Scenturion lures. In Virginia, on 14 July 2003, six traps with Scenturion lures captured nine males, whereas two traps containing a single, caged

female captured 91 moths (J.M. Sousa, unpublished data). In West Virginia between 25 and 29 July 2003, two traps with Scenturion lures caught 19 male dogwood borer and a single trap baited with a virgin female moth captured 135 males. Although (Z,Z)-3,13-ODDA is undoubtedly the main component of the dogwood borer sex pheromone, it is probable that the pheromone is comprised of additional compounds. Our data and the discrepant reports from previous studies on the response of male dogwood borer to different compounds, blends of compounds and commercial lures highlight the need for identiÞcation of the dogwood borer pheromone, as suggested by Tumlinson (1979) and Pfeiffer and Killian (1999). This would enable reÞnement and standardization of the monitoring system for dogwood borer and the development of predictive tools upon which management decisions could be based. In addition, the development and implementation of behaviorally based management strategies, including mating disruption and attract and kill, are contingent upon having a reliable monitoring system. In the only published study of mating disruption for dogwood borer, Pfeiffer and Killian (1999) deployed peachtree borer pheromone dispensers (Shin-Etsu Fine Chemical Co., Japan) in 2-ha plots of ÔGalaÕ apples in Virginia. The capture of males in pheromone traps was reduced by nearly 100% in three consecutive years, but more importantly, the percentage of burr knots on

April 2004


apple trees with dogwood borer larvae, pupal exuviae, or fresh frass was not reduced compared with conventionally managed blocks. Until the sex pheromone of the dogwood borer is isolated and characterized, it is likely that commercial lures for monitoring will remain suboptimal in their effectiveness, that results from Þeld trapping studies will continue to vary widely and that the development of alternative management tactics for it will be impaired. Acknowledgments We thank S. E. Wright, J. P. Engelman, Junying Nie, J. M. Sousa, and B. D. Short for excellent technical assistance and J. Fisher for providing pheromone lures for the concentration-response trials. We also thank M. Orr, R. Slonaker, J. Marker, and B. Swing and National Fruit Products Co. for cooperation and participation in these studies. Thanks also to H. Hogmire and D. Kain for an earlier review of this manuscript. This research was supported in part by a grant from the Virginia Agricultural Council and by the USDA CSREES Southern Region Integrated Pest Management program.

References Cited Alm, S. R., R. N. Williams, D. M. Pavuk, J. W. Snow, and M. A. Heinlein. 1989. Distribution and seasonal ßight activity of male grape root borers (Lepidoptera: Sesiidae) in Ohio. J. Econ. Entomol. 82: 1604 Ð1608. Anonymous. 2003a. Pherolist. Synanthedon scitula Harris http://nysaes.cornell.edu/pheronet/ins/synanscitu.html. Anonymous. 2003b. Spray bulletin for commercial tree fruit growers. Virginia, West Virginia and Maryland Cooperative Extension 2003. Virginia Polytechnic Institute and State University. Publ. 456-419. Barry, M. W., D. G. Nielsen, F. F. Purrington, and J. H. Tumlinson. 1978. Attractancy of pheromone blends to male peachtree borer, Synanthedon exitiosa. Environ. Entomol. 7: 1Ð3. Bergh, J. C., and Leskey T. C. 2002. Dogwood borer Þeld studies: preliminary data on seasonal phenology, monitoring and voltinism in Virginia and West Virginia, pp. 23Ð31. In P. W. Shearer [ed.], Proceedings of the 77th Annual Cumberland-Shenandoah Fruit Worker Conference, 15Ð16 November 2002, Winchester, VA. Bergh, J. C., and Leskey T. C. 2003. Biology, ecology, and management of dogwood borer in eastern apple orchards. Can. Entomol. 135: 615Ð 635. Braxton, S. M., and M. J. Raupp. 1995. An annotated checklist of clearwing borer pests of ornamental plants trapped using commercially available pheromone lures. J. Arbor. 21: 177Ð180. Davidson, J. A., S. A. Gill, and M. J. Raupp. 1992. Controlling clearwing moths with entomopathogenic nematodes: the dogwood borer case study. J. Arbor. 18: 81Ð 84. Eichlin, T. D., and W. D. Duckworth. 1988. Sesioidea: Sesiidae, pp. 1Ð176. In R. B. Dominick et al. [eds.], The moths of America North of Mexico fascicle 5.1. Wedge Entomological Research Foundation, Washington, DC. Eliason, E. A. and, D. A. Potter. 2000. Dogwood borer (Lepidoptera: Sesiidae) infestation of horned oak galls. J. Econ. Entomol. 93: 757Ð762. Engelhardt, G. P. 1932. Business proceedings of the eastern branch of the American Association of Economic Entomologists. J. Econ. Entomol. 25: 293Ð294.

351

Greenfield, M. D. 1978. Niche segregation of adult clearwing moths (Lepidoptera: Sesiidae) in Wisconsin. Ph.D dissertation, University of Wisconsin, Madison. Greenfield, M. D., and M. G. Karandinos. 1980. Resource partitioning of the sex pheromone communication channel in clearwing moths (Lepidoptera: Sesiidae) of Wisconsin. Ecol. Monogr. 49: 403Ð 426. Hogmire, H. W., Jr., ed. 1995. Mid-Atlantic orchard monitoring guide, publ. NRAES-75. Northeast Regional Agricultural Engineering Service, Ithaca, NY. Johnson, W. T., and H. H Lyon. 1991. Insects that feed on trees and shrubs, 2nd ed. Comstock, Ithaca, NY. Kain, D., and R. W. Straub. 2001. Status of borers infesting apple burr knots and their management in New York orchards. NY Fruit Q. 9: 10 Ð12. Karandinos, M. G., J. H. Tumlinson, and T. D. Eichlin. 1977. Field evidence of synergism and inhibition of the Sesiidae sex pheromone system. J. Chem. Ecol. 3: 57Ð 64. Leskey, T. C., and, J. C. Bergh. 2003. A simple character for sex differentiation of pupae and pupal exuviae of the dogwood borer (Lepidoptera: Sesiidae). Fla. Entomol. 86: 379 Ð381. Marini, R. P., M. L. Parker, J. A. Barden, and C. R. Unrath. 2003. The effect of eight dwarf rootstocks on burrknot development on ÔGalaÕ apple trees at two locations. J. Am. Pomol. Soc. 57: 93Ð96. Meyer, W. L., and W. S. Cranshaw. 1994. Capture of clearwing borers (Lepidoptera: Sesiidae) with three synthetic attractants in Colorado. Southwest. Entomol. 19: 71Ð76. Nielsen, D. G., F. F. Purrington, J. H. Tumlinson, R. E. Doolittle, and C. E. Yonce. 1975. Response of male clearwing moths to caged virgin females, female extracts, and synthetic sex attractants. Environ. Entomol. 4: 451Ð 454. Nielsen, D. G., F. F. Purrington, and G. F. Shambaugh. 1979. EAG and Þeld responses of sesiid males to sex pheromones and related compounds, pp. 11Ð26. In Pheromones of the Sesiidae. SEA-AR, ARR-NE-6. U.S. Dep. Agric. Washington, DC. Pfeiffer, D. G., and J. C. Killian. 1999. Dogwood borer (Lepidoptera: Sesiidae) ßight activity and an attempt to control damage in ÔGalaÕ apples using mating disruption. J. Entomol. Sci. 34: 210 Ð218. Riedl, H., R. W. Weires, A. Seaman, and S. A. Hoying. 1985. Seasonal biology and control of the dogwood borer, Synanthedon scitula (Lepidoptera: Sesiidae) on clonal apple rootstocks in New York. Can. Entomol. 117: 1367Ð 1377. Rogers, L. E., and J. F. Grant. 1990. Infestation levels of dogwood borer (Lepidoptera: Sesiidae) larvae on dogwood trees in selected habitats in Tennessee. J. Entomol. Sci. 25: 481Ð 485. Rom, R. C. 1970. Burr knot observations on clonal apple rootstocks in Arkansas. Fruit Var. Hortic. Dig. 24: 66 Ð 68. Rom, R. C. 1973. Burr knot characteristics of six clonal apple rootstocks. Fruit Var. J. 27: 84 Ð 86. SAS Institute. 1988. SAS/STAT userÕs guide, release 6.03 ed. SAS Institute, Cary, NC. Snow, J. W., T. D. Eichlin, and J. M. Tumlinson. 1985. Seasonal captures of clearwing moths (Sesiidae) in traps baited with various formulations of 3,13-octadecadienyl acetate and alcohol. J. Agric. Entomol. 2: 73Ð 84. Snow, J. W., M. Schwarz, and J. A. Klun. 1987. The attraction of the grape root borer, Vitacea polistiformis (Harris) (Lepidoptera: Sesiidae) to (E,Z)-2,13-octadecadienyl acetate and the effects of related isomers on attraction. J. Entomol. Sci. 4: 371Ð374.

352


Snow, J. W., D. T. Johnson, and J. R. Meyer. 1991. The seasonal occurrence of the grape root borer, (Lepidoptera: Sesiidae) in the eastern United States. J. Entomol. Sci. 26: 157Ð168. Taft, W. H., D. Smitley, and J. W. Snow. 1991. A guide to the clearwing borers (Sesiidae) of the north central United States. NC Region Ext. Publ. 394. Tumlinson, J. H., C. E. Yonce, R. E. Doolittle, R. R. Heath, C. R. Gentry, and E. R. Mitchell. 1974. Sex pheromones and reproductive isolation of the lesser peachtree borer and the peachtree borer. Science (Wash DC) 185: 614 Ð 616.

Vol. 97, no. 2

Tumlinson, J. H. 1979. The chemistry of Sesiidae pheromones, pp. 1Ð10. In Pheromones of the Sesiidae. SEA-AR, ARR-NE-6. U.S. Dep. Agric., Washington, DC. Warner, J., and S. Hay. 1985. Observations, monitoring, and control of clearwing borers (Lepidoptera: Sesiidae) on apple in central Ontario. Can. Entomol. 117: 1471Ð1478. Weires, R. 1986. Five years research and experience with control of dogwood borer and related burr knot problems. Compact Fruit Tree 19: 86 Ð 89. Received 19 May 2003; accepted 24 November 2003.