Optimizing Trap Design and Trapping Protocols for ...

Optimizing Trap Design and Trapping Protocols for Drosophila suzukii (Diptera: Drosophilidae) Author(s): Justin M. Renkema, Rosemarije Buitenhuis, and Rebecca H. Hallett Source: Journal of Economic Entomology, 107(6):2107-2118. 2014. Published By: Entomological Society of America URL: http://www.bioone.org/doi/full/10.1603/EC14254

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HORTICULTURAL ENTOMOLOGY

Optimizing Trap Design and Trapping Protocols for Drosophila suzukii (Diptera: Drosophilidae) JUSTIN M. RENKEMA,1,2 ROSEMARIJE BUITENHUIS,3

AND

REBECCA H. HALLETT1

J. Econ. Entomol. 107(6): 2107Ð2118 (2014); DOI: http://dx.doi.org/10.1603/EC14254

ABSTRACT Drosophila suzukii Matsumura (Diptera: Drosophilidae) is a recent invasive pest of fruit crops in North America and Europe. Carpophagous larvae render fruit unmarketable and may promote secondary rot-causing organisms. To monitor spread and develop programs to time application of controls, further work is needed to optimize trap design and trapping protocols for adult D. suzukii. We compared commercial traps and developed a new, easy-to-use plastic jar trap that performed well compared with other designs. For some trap types, increasing the entry area led to increased D. suzukii captures and improved selectivity for D. suzukii when populations were low. However, progressive entry area enlargement had diminishing returns, particularly for commercial traps. Unlike previous studies, we found putting holes in trap lids under a close-Þtting cover improved captures compared with holes on sides of traps. Also, red and black traps outperformed yellow and clear traps when traps of all colors were positioned 10 Ð15 cm apart above crop foliage. In smaller traps, attractant surface area and entry area, but not other trap features (e.g., headspace volume), appeared to affect D. suzukii captures. In the new, plastic jar trap, tripling attractant volume (360 vs 120 ml) and weekly attractant replacement resulted in the highest D. suzukii captures, but in the larger commercial trap these measures only increased by-catch of large-bodied Diptera. Overall, the plastic jar trap with large entry area is affordable, durable, and can hold high attractant volumes to maximize D. suzukii capture and selectivity. KEY WORDS spotted wing drosophila, trap design, attractant, color

Drosophila suzukii Matsumura (Diptera: Drosophilidae), commonly called spotted wing drosophila, was Þrst described in Japan and is recorded from other Asian countries; it was found in California and Spain in 2008 and has since spread across mainland North America and Europe (Kanzawa 1935, Hauser 2011, Calabria et al. 2012, Cini et al. 2012). Female D. suzukii ßies have a serrated ovipositor that allows them to lay eggs in ripe and ripening soft-skinned temperate fruit crops (Mitsui et al. 2006, Walsh et al. 2011). Developing larvae cause softening of fruit tissues, rendering fruit unmarketable and may promote rot-causing organisms, accelerating decomposition (Louis et al. 1996, Walsh et al. 2011). Under heavy infestations, up to 80% yield loss can occur (Lee et al. 2011); 20 and 37% losses in revenue were estimated in untreated California strawberries and raspberries, respectively (Goodhue et al. 2011), and over $26 million in crop losses were reported in the eastern United States in 2013 (Burrack 2014). As a response to the rapid spread and high economic impact of D. suzukii, considerable efforts are being made to develop monitoring and management pro1 School of Environmental Sciences, University of Guelph, 50 Stone Rd. E., Guelph, Ontario, Canada N1G 2W1. 2 Corresponding author, e-mail: [email protected]. 3 Vineland Research and Innovation Centre, 4890 Victoria Ave. N., Box 4000, Vineland Station, Ontario, Canada L0R 2E0.

grams. A number of insecticide classes are effective against D. suzukii, but application frequencies (5Ð14 d; Bruck et al. 2011) may increase both the risk that maximum insecticide residue limits are exceeded and the potential for resistance development. Cultural control methods such as removal of dropped or overripe fruit, removal of wild hosts from Þeld margins, and exclusion netting are recommended currently (Kawase et al. 2007, Walsh et al. 2011, Cini et al. 2012, Ontario Ministry of Agriculture, Food, and Rural Affairs [OMAFRA] 2014a), and biological control agents are under investigation (Chabert et al. 2012). To monitor D. suzukii, ßies can be easily trapped in homemade containers with entry holes and baited with affordable, moderately attractive liquids, such as apple cider vinegar, a yeastÐsugar solution, or whole wheat bread dough (e.g., Dreves and Langellotto-Rhodaback 2011, Eaton 2014, OMAFRA 2014b). However, trap designs and captures vary widely, with little standardization and utility for making management decisions. With the identiÞcation of a highly attractive lure (Cha et al. 2012, 2014), optimizing trap physical design, and developing trapping protocols, trapping should become more useful for monitoring and possibly for population reduction. Recently, a large, multi-state project was conducted to evaluate several trap types and designs and identify trap features that improved captures of and selectivity

0022-0493/14/2107Ð2118$04.00/0 䉷 2014 Entomological Society of America

2108 Table 1. Trap type Deli-cup Contech

Biobest Plastic jar a b

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Vol. 107, no. 6

Physical parameters and details of entry area modifications made to traps used for capturing D. suzukii Trap entry area (mm2)

Vol (ml)

Surface area of ACV (cm2)

Ht above ACV (cm)

Headspace above ACV (ml)a

64 128 2036 57 157 2,036 50 340 2010 2036

500

72

5.5

400

210

17

7.2

120

1100

83

14.5

1,520

1000

80

11.5

920

Entry points (on side)

Exp.

Nine 0.3-cm holes Eighteen 0.3-cm holes Eight 1.8-cm holes Two 0.6-cm holes Two 0.6-cm ⫹ two 0.8-cm holes Eight 1.8-cm holes Four 0.4-cm holes (in lid) Three 1.2-cm holes Three 1.2-cm ⫹ three 1.8-cm holes Eight 1.8-cm holes

A, B A, B, D A, B A, B, C A, B A, B E A, E A Ab, C, E

Calculated for experiment A; traps with 100 ml ACV. Evaluated in 2013 only.

for D. suzukii (Lee et al. 2012, 2013). It showed that trap types affect D. suzukii captures but not selectivity; traps with larger entry area captured more ßies than those with smaller entry areas (Landolt et al. 2011, Lee et al. 2012). However, entry area modiÞcations were not evaluated between traps of the same design. Surface area of liquid attractants within traps also appears to be an important trap feature, as increasing the surface area improved ßy captures (Lee et al. 2013). Keeping entry area and attractant surface area equal between different trap types will provide useful information on whether differences in other trap features (e.g., headspace, trap volume) affect D. suzukii captures. Color appears to be an important visual cue for D. suzukii, but the most attractive color for traps has not been established (Basoalto et al. 2013, Lee et al. 2013). Finally, mass trapping has been suggested for D. suzukii control (e.g., Cini et al. 2012). Effects of variables, such as attractant volume and replacement frequency, have not been assessed on D. suzukii captures but should provide useful information for developing mass trapping protocols. Field studies were conducted in 2012 and 2013 to improve trap design and trapping protocols for D. suzukii. Suggestions and issues arising from previous work (Lee et al. 2012, 2013; Basoalto et al. 2013) were used to address speciÞc trapping questions and provide new information for trap development. We tested whether increasing entry area in all traps would ubiquitously improve D. suzukii captures or selectivity (experiment A), whether other trap features affected D. suzukii captures when entry area and attractant surface area were equivalent (experiment B), and whether entry area position on traps affected D. suzukii captures (experiment C). Effect of trap color was tested in the Þeld, but traps were positioned close together so ßies were presented with all colors simultaneously (experiment D). Trap attractant volume and replacement frequency were altered to determine effects on D. suzukii captures and selectivity (experiment E). Materials and Methods Experiment A: Trap Type and Entry Area. Homemade deli-cup traps and 2012 models of commercially

available Contech Fruit Fly Traps (Contech Enterprises Inc., Victoria, BC, Canada) and Biobest Droso Traps (Biobest Canada Ltd., Leamington, ON, Canada) in 2012 and a homemade plastic jar trap in 2013 with modiÞed entry areas were evaluated (Table 1; Fig. 1). Clear deli-cups (Twinpak, Plastipak Industries Inc., Boucherville, QC, Canada) and plastic jars (Richards Packaging, Mississauga, ON, Canada) were wrapped with red tape (Cantech Industries Inc., Johnson City, TN), and plastic jars had a red plastic plate (22 cm in diameter) as a rain cover over the jar lid. Entry areas of different sizes were made with single hole punches in Deli-cup and modiÞed Contech traps (small holes: 0.3, 0.8 cm) or with hot metal punches (large holes: 1.8 cm), along sides of traps near the top. Metal hardware mesh (3 by 3 mm2 openings) in 2012 and Þberglass drywall tape (2.5 by 2.5 mm2 openings; Sheetrock, CGC Corp., Chicago, IL) in 2013 were glued over large holes. In modiÞed Biobest traps, the plastic inserts in holes (that reduced the entry area of each hole) were removed and mesh was glued over the holes. In modiÞed Contech traps, the red tubes inside the traps were removed. Traps were partially Þlled with 100 ml of apple cider vinegar (ACV; H.J. Heinz Co., Leamington, ON, Canada) and hung using plastic ties 2Ð3 m above the ground on tree branches in sweet cherry (Prunus avium L. ÔHeldenÞngenÕ and ÔLapinsÕ) and peach (Prunus persica (L.) Stokes ÔRedstarÕ) orchards near Niagara-on-the-Lake, Ontario (43⬚ 14⬘1⬙ N, 79⬚ 9⬘51⬙ W), and from bamboo garden stakes pushed into the ground at an angle so that traps were ⬍0.5 m above foliage of day-neutral strawberries (Fragaria x ananassa Duchesne ÔAlbionÕ) near Vineland, Ontario (2012: 43⬚ 10⬘1⬙ N, 79⬚ 20⬘29⬙ W; 2013: 43⬚ 10⬘17⬙ N, 79⬚ 21⬘38⬙ W). All crops were postharvest in 2012, and in 2013, cherries were postharvest, peaches were harvested a few days after traps were placed, and strawberries were being harvested. Unscented dish detergent (Selection, Metro Brands, Toronto, ON, Canada) was added to ACV (1 ml/liter) to reduce surface tension. Within each crop, traps were placed in a randomized complete block design (RCBD) with Þve blocks at least 25 m from each other. Within blocks, traps were 5 m apart (one trap per tree) in a 4 by 2 row grid in 2012 and a 3 by 3 row grid in 2013. Traps were

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Fig. 1. Homemade deli-cup (a, b) and plastic jar (g) and commercial Contech (c, d, e, f) and Biobest (h, i) traps with modiÞed entry areas (see Table 1 for entry areas) used to capture D. suzukii.

in place 6 Ð19 September 2012 and 19 AugustÐ7 September 2013 and serviced every 4 Ð5 d by emptying the contents, adding new ACV, and rerandomizing within blocks. Experiment B: Trap Type and Entry Area With Equivalent Attractant Surface Area. Two trap types with small (64 or 57 mm2), medium (128 or 157 mm2), or large (2036 mm2) entry areas (Table 1) and equivalent ACV surface area were evaluated in 2012. Small plastic cups (30 ml; Solo Cup Company, Lake Forest, IL) were held in place on bottoms of traps with small pieces of mounting putty (Lepage, Henkel Canada Corp., Mississauga, ON, Canada) and partially Þlled with 25 ml ACV (surface area ⫽ 12.6 cm2). Water (60 ml) with dish detergent was added to the trap surrounding the small plastic cup. Traps were hung on trellising string ⬇ 1 m above the ground in red raspberries (Rubus sp. ÔNovaÕ) near Waterloo, Ontario (43⬚ 29⬘57⬙ N, 80⬚ 38⬘14⬙ W) in an RCBD with seven blocks that were at least 15 m apart. Traps were 5 m apart within blocks in a 3 by 2 row grid. Traps were in place 5Ð13 October and serviced every 4 Ð5 d; ßies that drowned in ACV and water were collected. Experiment C: Entry Area Position. ModiÞed Contech traps, with holes in the lid and a larger, 7-cm-diameter red lid as a cover, were evaluated in 2013 and compared with unmodiÞed Contech and plastic jar traps (Table 1; Fig. 1). Traps were partially

Þlled with ACV (100 ml) and hung from trellising string ⬇ 1 m above the ground in fall red raspberries (Rubus sp. ÔAutumn BrittenÕ) at two locations: Milton (43⬚ 34⬘37⬙ N, 79⬚ 57⬘22⬙ W) and Vineland, Ontario (43⬚ 9⬘56⬙ N, 79⬚ 22⬘48⬙ W) in an RCBD with six replications at each site. Blocks were at least 15 m apart, and traps were 5 m apart along a single raspberry row within blocks. Traps were in place 24 SeptemberÐ 8 or 9 October (Milton or Vineland, respectively) and serviced every 4 Ð 6 d. Other Drosophila spp. in traps were not counted in this experiment. Experiment D: Trap Color. Four trap colors were evaluated in 2012 by spray painting deli-cups and lids (Table 1) red, black, or yellow (Rust-Oleum Corp., Vernon Hills, IL) or leaving them unsprayed (clear). Traps were partially Þlled with 120 ml ACV and hung 25 cm apart from 90 cm bamboo stakes that were secured horizontally on fence posts above foliage of fall red raspberries (Rubus sp. ÔAutumn BrittenÕ) near Milton, Ontario (43⬚ 34⬘37⬙ N, 79⬚ 57⬘22⬙ W). Each stake had one trap of each color. Trap color order was randomized along each stake and rerandomized each time traps were serviced. There were six replications with stakes spaced at least 25 m apart in randomly chosen locations throughout the Þeld. Traps were in place 24 OctoberÐ7 November and serviced weekly. Trap color was characterized with a colorimeter (CR Ð 400, Konica-Minolta, Ramsey, NJ) using the L*a*b* in-

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dices, where the L* value is 0 for black and 100 for white, a* is positive for red-purple and negative for bluish-green, and b* is positive for yellow and negative for blue (McGuire 1992). L*a*b* indices wereÑyellow traps, 86.11, ⫺6.27, 65.02; red traps, 41.89, 48.79, 29.53; and black traps, 24.62, 0.18, ⫺0.36. Experiment E: Trap Type and Attractant Volume and Replacement Frequency. Two trap types (Table 1) were evaluated in 2013 for effects of ACV volume and frequency of ACV replacement on numbers of D. suzukii and total by-catch. Traps were partially Þlled with either 120 or 360 ml ACV, and those with 360 ml were either serviced weekly or only at the end of the experiment. Traps were hung in fall red raspberries (Rubus sp. ÔPolanaÕ and ÔAutumn BrittenÕ) near Mt. Albert, Ontario (44⬚ 8⬘17⬙ N, 79⬚ 17⬘15⬙ W) from 24 SeptemberÐ15 October in an RCBD with Þve replications. Arrangement and servicing of traps was as described in experiment C; traps with 360 ml that were only emptied at the end of the experiment were rerandomized with the other traps within blocks each week. The by-catch (all non-D. suzukii individuals) was identiÞed to family and categorized by size as small, medium, or large (see Table 5 for details). Data Analysis. Captures over the entire trapping period were analyzed for experiments B, D, and E. Captures of D. suzukii were calculated per day for experiment C where the trapping period varied between sites and for experiment A where the trapping period varied year-to-year and because a few traps fell during certain trapping periods. Captures of male, female, total D. suzukii ßies, the proportion of D. suzukii out of total Drosophila bycatch (experiment A), and total by-catch sorted by size (experiment E) were analyzed using the standard least squares platform in JMP software (SAS Institute 2012; ␣ ⫽ 0.05) with Þxed and random effects. Fixed effects wereÑtrap type, crop, and trap type ⫻ crop (years analyzed separately) for experiment A; trap type, entry area, and trap type ⫻ entry area for experiment B; trap type, location, and trap type ⫻ location for experiment C; and trap type, attractant amount and replacement frequency, and trap type ⫻ amount and replacement frequency for experiment E. Blocks or blocks nested within crops or sites were random effects. Where trap type and crop or site interactions were signiÞcant, trap performance was subsequently analyzed for each crop or site. Residuals were checked for normality of error variance, and data were log (x) or square-root (x) transformed where necessary. Back-transformed lsmeans are shown; TukeyÕs honestly signiÞcant difference (HSD) tests were used to separate lsmeans or transformed lsmeans. For experiment D, numbers of D. suzukii in traps of different colors were compared using goodness-of-Þt G tests. The pooled G-test statistic is presented, as results were consistent between replicates (heterogeneity G-test, P ⬎ 0.05; McDonald 2009).

Vol. 107, no. 6 Results

Experiment A: Trap Type and Entry Area. Numbers of D. suzukii ßies captured in traps with varying entry areas differed signiÞcantly in both 2012 and 2013 (Fig. 2). More ßies were captured in deli-cup traps with the largest entry area than any other trap type in 2012. In 2013, plastic jar traps and deli-cup traps with largest entry area captured more ßies than other traps. In both years, captures in Contech traps were improved by increasing the entry area from 57 to 157 mm2, but not by a further increase from 157 to 2036 mm2. Increasing the entry area of Biobest traps did not improve ßy captures in either year. In 2012, the proportion of Drosophila spp. caught that were D. suzukii did not differ by trap type, but in 2013 higher proportions were generally found in traps with larger entry areas (Fig. 3). In 2012, captures of females differed due to the trap type and entry area ⫻ crop interaction (F14,84 ⫽ 2.7, P ⫽ 0.002), but captures of males did not (F14,84 ⫽ 1.5, P ⫽ 0.146). In 2013, captures differed signiÞcantly for both females (F16,96 ⫽ 3.6, P ⬍ 0.0001) and males (F16,96 ⫽ 5.7, P ⬍ 0.0001) due to the trap type and entry area ⫻ crop interaction. Main differences in male and female trap captures between crops in both years were due to efÞciency of Contech 156 mm2 compared with Contech 2,036 mm2, and magnitude of differences between the best traps (deli-cup 2,036 mm2 and plastic jar traps) compared with less effective traps (Tables 2Ð 4). Experiment B: Trap Type and Entry Area With Equivalent Attractant Surface Area. When attractant surface areas were equivalent, neither trap type nor the trap type ⫻ entry area interaction affected trap captures (Fig. 4). For female and total ßies, but not male ßies, D. suzukii captures increased with increasing entry area. There were signiÞcantly higher captures in traps with largest (2,036 mm2) compared with smallest (57 or 64 mm2) entry areas. Proportion of D. suzukii out of all Drosophila spp. (71Ð 83%) was not signiÞcantly affected by trap type (F1,29 ⫽ 1.6, P ⫽ 0.212), entry area (F2,29 ⫽ 0.1, P ⫽ 0.941), or their interaction (F2,30 ⫽ 0.2, P ⫽ 0.842). Experiment C: Entry Area Position. Numbers of male, female, and total D. suzukii ßies captured differed signiÞcantly between trap types and locations, but the trap type ⫻ location interaction was only signiÞcant for total ßies (Fig. 5). About eight times more total ßies were captured in modiÞed (four holes in lids) than unmodiÞed Contech traps, and about double the number of ßies was captured in plastic jar traps than modiÞed Contech traps. When male and female ßies were analyzed separately, plastic jar traps did not capture more ßies than modiÞed Contech traps (Fig. 5). More total ßies were captured at Milton (33.9 ⫾ 6.7/8.2) than at Vineland (7.3 ⫾ 1.4/1.7; lsmeans ⫾ 95% CI). The signiÞcant trap type ⫻ location interaction was due to more total ßies captured in plastic jar traps than modiÞed Contech traps at Milton, but not at Vineland.

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Fig. 2. Mean (⫾95% CI) numbers of D. suzukii captured in four trap types with varying entry areas (mm2) in three crops (cherries, peaches, and strawberries) in the Niagara region, Ontario, experiment A in (a) 2012 (trap F7,84 ⫽ 36.3, P ⬍ 0.0001; crop F2,12 ⫽ 12.2, P ⫽ 0.001; trap ⫻ crop F14,84 ⫽ 2.3, P ⫽ 0.009) and (b) 2013 (trap F8,96 ⫽ 37.3, P ⬍ 0.0001; crop F2,12 ⫽ 88.4, P ⬍ 0.0001; trap ⫻ crop F16,96 ⫽ 5.7, P ⬍ 0.0001). Plastic jar traps tested only in 2013. Arrows indicate unmodiÞed commercial traps. Back-transformed lsmeans are shown; bars with the same letter in each panel are not signiÞcantly different (TukeyÕs HSD test, ␣ ⫽ 0.05).

Experiment D: Trap Color. Male, female, and total D. suzukii ßy captures varied signiÞcantly due to trap color (Fig. 6). Red and black traps captured more ßies than clear or yellow traps. The proportion of Drosophila spp. caught that were D. suzukii was not signiÞcantly affected by trap color (␹2 ⫽ 1.5, df ⫽ 3, P ⫽ 0.684), although percent D. suzukii in red and black (86 and 84%) traps was ⬇10% greater than that in yellow and clear traps (74 and 75%). Experiment E: Trap Type and Attractant Volume and Replacement Frequency. Trap type and attractant amount and replacement frequency signiÞcantly affected numbers of and percent D. suzukii captured (Fig. 7). More D. suzukii were captured in plastic jar traps with 360 ml of ACV replaced weekly than in all other trap and amount and replacement frequency combinations. Plastic jar traps captured a higher percentage of D. suzukii than Biobest traps. Plastic jar traps with 360 ml ACV replaced weekly had a higher

proportion of D. suzukii out of the total by-catch than those with 120 ml replaced weekly or 360 ml not replaced. The by-catch in traps consisted mainly of beetles (Coleoptera) and ßies (Diptera). The large majority of beetle by-catch was sap beetles (Nitidulidae), and plastic jar traps with 360 ml ACV replaced weekly captured more nitidulids than most other trap types and amount and replacement frequency combinations (Table 5). Large-sized by-catch was dominated by blow ßies (Calliphoridae) that were almost exclusively captured in Biobest traps and in higher numbers when 360 ml ACV was replaced weekly in Biobest traps compared with 360 ml that was not replaced. The by-catch of medium-sized Diptera was more than double in Biobest than plastic jar traps and more than two to three times greater in traps with 360 ml ACV replaced weekly than others. Small-sized by-catch in plastic jar traps was nearly double that of Biobest traps

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Fig. 3. Mean (⫾95% CI) percent D. suzukii of all Drosophila spp. captured in four trap types with varying entry areas (mm2) in three crops (cherries, peaches, and strawberries) in the Niagara region, Ontario, experiment A in (a) 2012 (trap F7,84 ⫽ 2.0, P ⫽ 0.067; crop F2,12 ⫽ 89.7, P ⬍ 0.0001; trap ⫻ crop F14,84 ⫽ 0.6, P ⫽ 0.844) and (b) 2013 (trap F8,96 ⫽ 7.1, P ⬍ 0.0001; crop F2,12 ⫽ 55.4, P ⬍ 0.0001; trap ⫻ crop F16,96 ⫽ 1.6, P ⫽ 0.083). Plastic jar traps tested only in 2013. Arrows indicate unmodiÞed commercial traps. Back-transformed lsmeans are shown; bars with the same letter in each panel are not signiÞcantly different (TukeyÕs HSD test, ␣ ⫽ 0.05).

and was greater in traps with 360 ml ACV replaced weekly than others. Discussion Improving trap design and trapping protocol, along with other methods and developments (e.g., detection of larvae in ripe fruit, highly attractive lures), will increase the utility of trap capture data for monitoring the range expansion of D. suzukii and making management decisions where this pest severely impacts

soft-skinned fruit. Here we show that trap entry area size and placement, liquid attractant surface area, attractant volume and replacement frequency, and trap color affect D. suzukii captures. Our results differ from those of previous D. suzukii trapping studies (Lee et al. 2012, 2013; Basoalto et al. 2013) by showing that entry area enlargement has diminishing returns, traps with entry holes on lids capture more ßies, and that red and black traps improve captures compared with yellow traps. We have developed an easy-to-use homemade trap that with increased volume and frequent

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Table 2. Mean (95% CI) numbers of female D. suzukii captured per trap per day in three trap types with varying entry areas in three postharvest fruit crops, Niagara region, Ontario, 6 –19 September 2012, experiment A Trap type

Entry area (mm2)

Deli-cup

64 128 2,036 57 157 2,036 340 2,010

Contech Biobest F7,28 P

Cherries

Peaches

Strawberries

1.0 (0.6Ð1.7)c 2.2 (1.3Ð3.5)bc 5.0 (3.1Ð8.2)a 1.1 (0.7Ð1.8)c 3.7 (2.3Ð5.9)ab 2.9 (1.8Ð4.7)ab 1.8 (1.1Ð2.9)bc 2.2 (1.4Ð3.6)bc 10.5 ⬍ 0.0001

0.8 (0.6Ð1.1)b 0.9 (0.6Ð1.2)b 2.8 (2.0Ð3.8)a 0.8 (0.6Ð1.1)b 2.7 (2.0Ð3.8)a 1.5 (1.1Ð2.0)ab 1.1 (0.8Ð1.6)b 1.1 (0.8Ð1.5)b 10.4 ⬍ 0.0001

0.4 (0.3Ð0.7)de 1.1 (0.7Ð1.7)bc 3.1 (2.0Ð4.6)a 0.3 (0.2Ð0.5)e 1.1 (0.7Ð1.6)bc 2.1 (1.4Ð3.1)ab 0.8 (0.5Ð1.1)cd 1.3 (0.9Ð2.0)abc 17.5 ⬍ 0.0001

Means in the same column with the same letter are not signiÞcantly different, TukeyÕs HSD test, ␣ ⫽ 0.05.

replacement of liquid attractant captures more D. suzukii and fewer nontarget organisms than a commercial trap. Based on results of Lee et al. (2012), we expected improved trap captures of D. suzukii with increased entry area of the three trap types examined in this study. Indeed we found that increasing the entry area from 64 to 2,036 mm2 in deli-cup traps resulted in a fourfold and over threefold increase in captures in 2012 and 2013, respectively. However, increasing the entry area from 340 to 2,010 mm2 in Biobest traps resulted in a small, nonsigniÞcant gain in captures. It is likely that there is a diminishing rate of increasing captures with increased entry area (Lee et al. 2012), as increasing Contech trap entry area from 57 to 156 mm2 (and removing the red tube) signiÞcantly improved captures, but a further increase to 2,036 mm2 had no effect in 2012 and little effect in 2013. A diminishing rate of increase may also depend on initial (unmodiÞed) trap entry area and other trap characteristics (e.g., attractant surface area, trap size). The position of entry holes affected D. suzukii captures, as four holes (50 mm2) in the lid of Contech traps resulted in D. suzukii captures that were approximately eight times higher than those in unmodiÞed Table 3. Mean (95% CI) numbers of male D. suzukii captured per trap per day in four trap types with varying entry areas in three fruit crops, Niagara region, Ontario, 19 August–7 September 2013, experiment A area Trap type Entry (mm2) Deli-cup Contech Biobest Plastic jar F8,32 P

64 128 2036 57 157 2036 340 2010 2036

Cherriesa

Peachesb

Strawberriesc

0.4 (0.2Ð0.6)cd 0.4 (0.2Ð0.6)cd 1.7 (1.3Ð2.1)a 0.2 (0.1Ð0.4)d 0.8 (0.6Ð1.1)bc 1.0 (0.7Ð1.3)ab 0.4 (0.2Ð0.6)cd 0.4 (0.2Ð0.6)d 1.3 (1.0Ð1.7)ab 20.2 ⬍ 0.0001

0.1 (0.0Ð0.4)abc 0.2 (0.0Ð0.5)abc 0.6 (0.2Ð1.0)a 0.0 (0.0Ð0.2)c 0.1 (0.0Ð0.2)bc 0.4 (0.1Ð0.8)ab 0.1 (0.0Ð0.4)abc 0.1 (0.0Ð0.3)abc 0.4 (0.2Ð0.9)ab 22.8 ⬍ 0.0001

0.000 0.000 0.012 (0.001Ð0.039) 0.000 0.000 0.004 (0.000Ð0.023) 0.000 0.004 (0.000Ð0.023) 0.008 (0.000Ð0.032) 1.2 0.357

Means in the same column with the same letter are not signiÞcantly different, TukeyÕs HSD test, ␣ ⫽ 0.05. a Postharvest. b Harvest to postharvest. c During harvest.

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Table 4. Mean (95% CI) numbers of female D. suzukii captured per trap per day in four trap types with varying entry areas in three fruit crops, Niagara region, Ontario, 19 August–7 September 2013, experiment A area Trap type Entry (mm2) Deli-cup Contech Biobest Plastic jar F8,32 P

64 128 2,036 57 157 2,036 340 2,010 2036

Cherriesa

Peachesb

Strawberriesc

0.6 (0.4Ð1.0)c 0.8 (0.5Ð1.2)c 2.9 (2.3Ð3.6)a 0.5 (0.2Ð0.8)c 1.9 (1.4Ð2.5)ab 1.8 (1.3Ð2.4)ab 0.6 (0.4Ð1.0)c 1.0 (0.7Ð1.5)bc 3.0 (2.3Ð3.7)a 22.8 ⬍ 0.0001

0.2 (0.1Ð0.4)bc 0.2 (0.1Ð0.4)bc 0.8 (0.5Ð1.1)a 0.1 (0.0Ð0.3)c 0.3 (0.1Ð0.5)bc 0.5 (0.3Ð0.8)ab 0.1 (0.0Ð0.3)c 0.1 (0.0Ð0.3)c 0.9 (0.6Ð1.3)a 12.9 ⬍ 0.0001

0.000c 0.002 (0.006Ð0.029)bc 0.120 (0.050Ð0.221)a 0.002 (0.006Ð0.029)bc 0.025 (0.001Ð0.078)abc 0.066 (0.018Ð0.144)ab 0.002 (0.006Ð0.029)bc 0.036 (0.005Ð0.098)abc 0.042 (0.007Ð0.107)abc 4.9 0.0005

Means in the same column with the same letter are not signiÞcantly different, TukeyÕs HSD test, ␣ ⫽ 0.05. a Postharvest. b Harvest to postharvest. c During harvest.

Contech traps with two holes (57 mm2) on the trap sides. This result is opposite to what Lee et al. (2013) found, where side-entry traps captured four to seven times more ßies than traps with covered top entries. The trap entry area and the distance between the lid and the cover were larger in the Lee et al. (2013) study than this experiment. A larger distance between cover and trap may have allowed rain to enter traps, thus diluting the attractant and reducing attractiveness compared with side-entry traps. The proximity and larger diameters of Contech covers relative to the trap lids likely prevented any rain from entering traps. However, in this study plastic jar traps with side entries and covers still captured twice as many D. suzukii ßies than Contech traps with holes in lids. The surface area of liquid attractants in traps can affect D. suzukii captures, as increasing ACV surface area from 40 to 90 cm2 resulted in 12% more captures (Lee et al. 2013). In the current study, when surface area was equivalent between two trap types, deli-cups and Contech, differences in D. suzukii captures depended only on entry area. Other trap features that differ between deli-cup and Contech designs, such as height above attractant and headspace, did not appear to affect captures. Therefore, fewer captures in Contech than deli-cup traps when both had entry areas of 2,036 mm2 (experiment A), may be explained by the larger attractant surface area in deli-cup than Contech traps (72 vs 17 cm2). However, despite having large entry and attractant surface areas, Biobest traps performed poorly in experiment A, meaning too large headspace or height above attractant could negatively affect D. suzukii captures. Due to the design of the 2012 Biobest trap, which did not have a ßat bottom, it was not possible to manipulate the attractant surface area. Improved trap sensitivity is required for accurate monitoring of D. suzukii at low population levels to time control measures. We found the same trends in D. suzukii capture rates among trap types and entry areas in 2013 (earlier in the season, lower captures) as in 2012 (later in the season, higher captures). In straw-

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Fig. 4. Mean (⫾95% CI) numbers of D. suzukii captured in two trap types (deli-cups, Contech; data pooled) with varying entry area sizes (small: 57 or 64 mm2; medium: 128 or 156 mm2; large: 2036 mm2) and equal attractant surface area per trap (12.6 cm2) in fall red raspberries near Waterloo, Ontario, experiment B. Comparisons for Males: trap type F1,29 ⫽ 0.39, P ⫽ 0.535; entry area F2,29 ⫽ 0.50, P ⫽ 0.615; trap ⫻ area F2,29 ⫽ 1.06, P ⫽ 0.359; Females: trap type F1,29 ⫽ 2.02, P ⫽ 0.166; entry area F2,29 ⫽ 7.49, P ⫽ 0.002; trap ⫻ area F 2,29 ⫽ 0.98, P ⫽ 0.388; Total ßies: trap type F1,29 ⫽ 0.64, P ⫽ 0.429; entry area F2,29 ⫽ 4.29, P ⫽ 0.023; trap ⫻ area F 2,29 ⫽ 0.10, P ⫽ 0.909. Back-transformed lsmeans are shown; bars with the same letter of the same case are not signiÞcantly different (TukeyÕs HSD test, ␣ ⫽ 0.05).

berries in 2013, no or very low male and female captures in traps with small entry areas would have resulted in a recommendation for no D. suzukii management, whereas higher captures in traps with larger entry areas would have supported a decision to control for D. suzukii at that time. SigniÞcant trap type and entry area differences among sites or crops for captures of males or female ßies appeared to be due largely to differences in captures between modiÞed Contech traps (156 vs 2036 mm2). Therefore, regardless of crop (postharvest peaches or cherries versus ripening strawberries) or hanging method (tree branches in shade versus bamboo stakes in an open strawberry Þeld), deli-cup or plastic jar traps with large entry areas performed best. Trap selectivity is also important for early season monitoring and ease of sorting samples. We found little difference in trap selectivity in 2012, when all traps captured 20 Ð30% D. suzukii out of total Dro-

sophila spp., but in 2013 when D. suzukii proportions were only 0.5Ð2.5%, traps that captured more Drosophila spp. also captured higher proportions of D. suzukii. To our knowledge, this is the Þrst report of a difference in trap design affecting selectivity, as previous studies found equal proportions of D. suzukii among trap types with 10 Ð70% D. suzukii (Lee et al. 2012, 2103; Basoalto et al. 2013). In experiment E with plastic jar and Biobest traps, a similar pattern was observed, with fewer captures and lower selectivity in Biobest than in plastic jar traps. Plastic jar traps with mesh over the holes prevented captures of large- and many medium-sized Diptera, including almost all Calliphoridae that were abundant, as this site was adjacent to pasture. Use of mesh over holes shifted the distribution of the by-catch to small Diptera, as almost twice as many small Diptera were captured in plastic jar traps than Biobest traps. The time it took to process samples was not recorded, but we noted it was less

Fig. 5. Mean (⫾95% CI) numbers of D. suzukii captured in three trap types 24 SeptemberÐ8 or 9 October 2013 in fall red raspberries near Milton and Vineland, Ontario, experiment C. Comparisons for Males: trap type F1,20 ⫽ 56.9, P ⬍ 0.0001; site F1,10 ⫽ 50.7, P ⬍ 0.0001; trap ⫻ site F2,20 ⫽ 2.6, P ⫽ 0.096; Females: trap type F1,20 ⫽ 36.3, P ⬍ 0.0001; site F1,10 ⫽ 171.1, P ⬍ 0.0001; trap ⫻ site F2,20 ⫽ 0.9, P ⫽ 0.443; Total ßies: trap type F2,20 ⫽ 3.7, P ⫽ 0.043; site F1,10 ⫽ 149.5, P ⬍ 0.0001; trap ⫻ site F2,20 ⫽ 121.6, P ⬍ 0.0001. Back-transformed lsmeans are shown; bars with the same letter of the same case in the same font style are not signiÞcantly different (TukeyÕs HSD test, ␣ ⫽ 0.05).

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Fig. 6. Total numbers of D. suzukii captured in deli-cup traps that were unpainted (clear) or painted (yellow, black, or red) and hung in groups with one trap of each color above foliage of fall red raspberries near Milton, Ontario, experiment D. Comparisons for Males: ␹2 ⫽ 1378.8, df ⫽ 3, P ⬍ 0.0001; Females: ␹2 ⫽ 1107.3, df ⫽ 3, P ⬍ 0.0001; Total ßies: ␹2 ⫽ 2466.7, df ⫽ 3, P ⬍ 0.0001. Percent D. suzukii captures out of total D. suzukii captures is above each bar.

time consuming to separate D. suzukii from other small ßies than searching for and removing them when they adhered to the bodies of large ßies.

We hypothesized that captures in large traps (Biobest, plastic jar) could be improved by adding more attractant, in this case ACV, and that with in-

Fig. 7. Mean (⫾SE) (a) numbers and (b) percent D. suzukii out of all by-catch in two trap types (Biobest, Plastic jar) 24 SeptemberÐ15 October in fall red raspberries near Mt. Albert, Ontario, experiment E. Apple cider vinegar in traps (120 or 360 ml) was replaced weekly or not replaced (360 ml) for 3 wk. Comparisons for D. suzukii captures: trap type F1,20 ⫽ 38.9, P ⬍ 0.0001; amount and replacement frequency F2,20 ⫽ 17.5, P ⬍ 0.0001; trap type ⫻ amount and replacement frequency F1,20 ⫽ 12.0, P ⫽ 0.0004, and for percent D. suzukii: trap type F2,20 ⫽ 124.9, P ⬍ 0.0001; amount and replacement frequency F2,20 ⫽ 2.4, P ⫽ 0.12; trap type ⫻ amount and replacement frequency F2,20 ⫽ 7.8, P ⫽ 0.003. Bars with the same letter in each panel are not signiÞcantly different (TukeyÕs HSD test, ␣ ⫽ 0.05.

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Table 5. Mean (95% CI) numbers of non-D.suzukii individuals captured over 3 wk in two trap types with differing amounts and replacement frequency of apple cider vinegar in fall red raspberries, Mt. Albert, Ontario, 24-September–15 October, experiment E Trap type

Amount (ml) and replace. freq.

Biobest Plastic jar

Biobest Plastic jar Trap type Amount Trap ⫻ amt

120 weekly 360 weekly 360 not replaced 120 weekly 360 weekly 360 not replaced 120 weekly 360 weekly 360 not replaced F1,20 P F2,20 P F2,20 P

Coleopteraa 29.4 (16.7Ð45.6) 37.5 (23.0Ð55.5) 30.0 (16.6Ð47.2) 40.6 (24.8Ð60.3) 29.9 (16.6Ð47.1) 36.2 (18.9Ð59.1)ab 24.4 (10.7Ð43.6)b 28.1 (13.2Ð48.6)b 24.3 (10.6Ð43.5)b 60.9 (37.7Ð89.7)a 31.7 (15.7Ð53.3)b 1.6 0.226 1.1 0.339 4.2 0.029

Diptera, Hymenoptera, and Lepidoptera Largeb

Mediumc

Smalld

89.7 (65.0Ð118.5)a 0.5 (0.5Ð4.6)b 30.6 (15.7Ð50.5)ab 40.0 (22.8Ð62.4)a 11.8 (3.5Ð25.1)b 102.4 (64.9Ð148.4)ab 151.5 (104.9Ð206.5)a 35.9 (15.4Ð64.9)b 0.9 (1.2Ð9.1)c 0.1 (3.0Ð5.8)c 0.8 (1.4Ð8.7)c 127.9 ⬍ 0.0001 5.0 0.018 6.6 0.006

77.1 (60.7Ð95.5)a 32.5 (22.2Ð44.8)b 45.9 (31.3Ð63.2)b 94.8 (75.2Ð119.1)a 27.3 (16.4Ð41.0)b 78.6 (52.0Ð110.7) 134.2 (98.6Ð175.3) 34.8 (18.0Ð57.0) 21.9 (9.1Ð40.1) 62.2 (38.8Ð91.0) 20.7 (8.4Ð38.5) 21.9 0.0001 16.2 ⬍ 0.0001 1.8 0.1935

151.1 (105.7Ð204.5)b 280.3 (217.1Ð351.5)a 203.1 (144.9Ð271.0)b 325.2 (250.3Ð409.9)a 126.9 (81.9Ð181.6)b 161.5 (97.1Ð242.2) 223.9 (146.7Ð317.4) 84.7 (40.3Ð145.3) 249.4 (167.4Ð347Ð6) 177.7 (333.1Ð573.9) 445.4 (109.8Ð261.9) 17.9 0.0004 13.8 0.0002 0.7 0.495

Means in the same column with the same letter are not signiÞcantly different, TukeyÕs HSD test, ␣ ⫽ 0.05. a NitidulidaeÑ96.6%; Other ColeopteraÑ3.4%. b Large: CalliphoridaeÑ91.6%; ApidaeÑ1.8%; LepidopteraÑ 0.8%; Other DipteraÑ5.8%. c Medium: Muscidae and AnthomyiidaeÑ55.2%; AnisopodidaeÑ 44.8%. d Small: Drosophila spp.Ñ 49.6%; ChloropidaeÑ25.4%; ScatopsidaeÑ9.8%; SciaridaeÑ 8.0%; Proctotrupidae and BraconidaeÑ2.3%; Other DipteraÑ 4.9%.

creased volume, replacement frequency could be reduced without compromising D. suzukii captures. Tripling the amount of ACV in plastic jar traps (360 vs 120 ml) improved D. suzukii captures by about three times and selectivity by ⬇5% with weekly replacement; however, the same increase in ACV volume did not improve D. suzukii captures in Biobest traps. We observed that the large by-catch of large- and mediumsized Diptera ßoated on the ACV and suspect that as a result, D. suzukii were less likely to drown and more likely able to escape from Biobest traps through the large unscreened entry holes. Not replacing 360 ml ACV for 3 wk resulted in much lower captures in plastic jar traps than with weekly replacement of 360 ml of ACV, but less of an effect was detected in Biobest traps. Before placing traps at this location (24 SeptemberÐ15 October), D. suzukii was managed with Delegate (spinetoram) on 2 and 8 September and malathion on 16 September at recommended rates. As a result, captures were low the Þrst week (24 SeptemberÐ1 October) and four to Þve times higher in the third and second weeks, respectively (data not shown). Therefore, as D. suzukii numbers increased, ACV aged and likely became a less potent attractant. However, traps without replacement of 360 ml of ACV captured almost as many D. suzukii as those with 120 ml replaced weekly; therefore, time required for servicing traps was reduced without compromising captures. There was a signiÞcant difference in both male and female D. suzukii captures among traps of different colors. As in laboratory choice experiments (Basoalto et al. 2013), ßies appear to be attracted to red and black more than yellow when given a choice of trap color in the Þeld. Lee et al. (2013) reported that when traps were hung in shady spots and spaced 2Ð3 m apart, yellow traps captured more D. suzukii ßies than other colors; captures were 1.5 times higher in yellow than

clear traps that had the fewest captures of all colors. Differences in color hues may help explain capture efÞciency differences. Our yellow traps were lighter in hue (L*a*b* ⫽ 86.11, ⫺6.27, 65.02) than those used by Lee et al. (2013) (74.23, ⫺2.21, 64.01), and our red traps (41.89, 48.79, 29.53) had a greater a* value (increased red-purple intensity) than theirs (38.03, 35.15, 19.06). As with other fruit-infesting ßies (Diptera: Tephritidae, Rhagoletis spp.), attractiveness to trap colors may be inßuenced by crop type or change with fruit maturity (Liburd et al. 1998, Henneman and Papaj 1999, Mayer et al. 2000) or be related to trap age, as colors may fade throughout the trapping season. Dark colors, red and black, may be more attractive to D. suzukii in Þelds with ripe, similarly colored fruit, as was the case in this experiment. At a few locations with ripe fruit or postharvest, red traps captured more ßies than yellow or traps of other colors (Lee et al. 2013). However, we suspect that differences in our results and those of Lee et al. (2013) are mainly due to how traps were positioned. Trap color may not be as important as the attractant for capturing D. suzukii. Flies will enter traps with ACV at relatively similar rates when they do not perceive various colors simultaneously (traps spaced 2Ð3 m apart, Lee et al. 2013). When traps containing the same attractant are near each other (25 cm apart, this experiment) color becomes a signiÞcant factor, resulting in captures in red traps that were seven times higher than in yellow traps. Traps in our experiment were placed above raspberry foliage, where colors may contrast more sharply with background colors (blue sky, white or gray clouds), changing their relative attractiveness to ßies that are below in foliage, than colors in shady crop areas where lower contrasts with background colors may occur. Therefore, further investigation is needed to determine whether ßy captures are greater in red or dark colored

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December 2014

traps placed above foliage compared with yellow or other colored traps placed within the crop canopy. An ideal trap should also be cost-effective, easy-touse, and durable. The commercial traps cost more (Contech Fruit Fly Trap: $5 CDN, Biobest Droso Trap: $6.50 CDN) than the materials plus labor costs for our homemade traps (materials for deli-cup trap with large holes and mesh: $0.40 CDN, plastic jar trap: $2 CDN; labor is $0.17 CDN per trap for both types at 20 traps made per hour and $10 per hour). Despite being cost-efÞcient, deli-cup traps with two plastic ties were not as easy to hang from branches or stakes than traps with a single plastic tie. Plastic deli-cups also become brittle, and traps are not reusable after a season, unlike commercial traps. The homemade, plastic jar traps are durable, except red plastic plates used as covers cracked and red tape faded, thus requiring replacement each season. ModiÞcation to some commercial traps have been made since these experiments were conducted, which may have improved trap efÞciency. However, we recommend that the plastic jar trap or very similar designs be used for future D. suzukii trapping, based on its performance in 2013 experiments, ease-of-use (to service trap, jar can be unscrewed from lid without removing plastic tie from branch or stake), relative durability, ability to hold a large volume of attractant, and moderate price. Furthermore, the relative efÞcacy of these traps at low D. suzukii levels suggests that they may be suitable for use in early detection of D. suzukii as well as for population monitoring to time pest management actions. In conclusion, traps for D. suzukii should maximize entry area, although designs with large containers and large entry areas (⬇350 mm2) will likely not be improved by further increasing the entry area. Attractant surface area should also be maximized (Lee et al. 2013) and is likely more important than other trap features (e.g., headspace volume) in affecting D. suzukii captures, at least in smaller traps like those tested in this study. Larger traps are advantageous, as they can hold more liquid attractant, resulting in greater captures, reduced servicing time, or both, but large holes in large traps should be covered with mesh to exclude larger-bodied by-catch. However, certain features of large traps, particularly the large headspace volume in the Biobest traps evaluated herein, may facilitate D. suzukii survival in and eventual escape from traps. Captures of D. suzukii were greater in red or black compared with yellow or clear traps and in traps with holes in lids compared with those with holes on trap sides, but these Þndings are not consistent with previous studies and require further testing. Acknowledgments We thank Contech Enterprises Inc. and Biobest Canada Ltd. for providing traps; Scott MacSween, Jeff Tigchelaar, Bert Andrews, Alvin Brooks, Louis Rotierre, and Anne Nauman for access to Þelds; Jordan Hazell, Zachariah Telfer, Emily Anderson, Caitlyn Schwenker, Taylor LaPlante, Chris House, Karen Heal, Angela Brommit, Kevin Reeh, and Erfan Vafaie for technical assistance; and John Cline (University of

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Guelph) for use of colorimeter. This research was funded by the University of GuelphÐOntario Ministry of Agriculture, Food and Rural Affairs Sustainable Production Program awarded to R.H.H. and R.B. and a Webster Postdoctoral Fellowship, School of Environmental Sciences, University of Guelph, awarded to J.M.R.

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Kawase, S., K. Uchino, and K. Takahashi. 2007. Control of cherry drosophila, Drosophila suzukii, injurious to blueberry. Plant Prot. 61: 205Ð209. Landolt, P. J., T. Adams, and H. Rogg. 2011. Trapping spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), with combinations of vinegar and wine, and acetic acid and ethanol. J. Appl. Entomol. 136: 148 Ð154. Lee, J. C., D. J. Bruck, A. J. Dreves, C. Loriatti, H. Vogt, and P. Baufeld. 2011. In focus: spotted wing drosophila, Drosophila suzukii, across perspectives. Pest Manage. Sci. 67: 1349 Ð1351. Lee, J. C., H. J. Burrack, L. D. Barrantes, E. H. Beers, A. J. Dreves, K. A. Hamby, D. R. Haviland, R. Isaacs, T. A. Richardson, P. W. Shearer, et al. 2012. Evaluation of monitoring traps for Drosophila suzukii (Diptera: Drosophilidae) in North America. J. Econ. Entomol. 105: 1350 Ð 1357. Lee, J. C., P. W. Shearer, L. D. Barrantes, E. H. Beers, H. J. Burrack, D. T. Dalton, A. J. Dreves, L. J. Gut, K. A. Hamby, D. R. Haviland, et al. 2013. Trap designs for monitoring Drosophila suzukii (Diptera: Drosophilidae). Environ. Entomol. 42: 1348 Ð1355. Liburd, O. E., S. R. Alm, R. A. Casagrande, and S. Polavarapu. 1998. Effect of trap color, bait, shape and orientation in attraction of blueberry maggot (Diptera: Tephritidae). J. Econ. Entomol. 91: 243Ð249. Louis, C., M. Girard, G. Kuhl, and M. Lopez-Ferber. 1996. Persistence of Botrytis cinerea in its vector Drosophila melanogaster. Phytopathology 86: 934 Ð939.

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Mayer, D. F., L. E. Long, T. J. Smith, J. Olsen, H. Riedl, R. R. Heath, T. C. Leskey, and R. J. Prokopy. 2000. Attraction of adult Rhagoletis indifferens (Diptera: Tephritidae) to unbaited and odor-baited red spheres and yellow rectangles. J. Econ. Entomol. 93: 347Ð351. McDonald, J. H. 2009. Handbook of biological statistics, 2nd ed. Sparky House Publishing, Baltimore, MD. McGuire, R. G. 1992. Reporting of objective color measurements. HortScience 27: 1254 Ð1255. Mitsui, H., K. H. Takahashi, and M. T. Kimura. 2006. Spatial distributions and clutch size of Drosophila species ovipositing on cherry fruits of different stages. Popul. Ecol. 48: 233Ð237. (OMAFRA) Ontario Ministry of Agriculture, Food, and Rural Affairs. 2014a. Management guidelines for spotted wing drosophila in Ontario. (http://www.omafra.gov. on.ca/english/crops/facts/swd-management.htm). (OMAFRA) Ontario Ministry of Agriculture, Food, and Rural Affairs. 2014b. Monitoring for spotted wing drosophila in Ontario. (http://www.omafra.gov.on.ca/english/ crops/facts/swd-monitor.htm). SAS Institute. 2012. JMP, version 10.0.2. SAS Institute, Cary, NC. Walsh, D. B., M. P. Bolda, R. E. Goodhue, A. J. Dreves, J. Lee, D. J. Bruck, V. M. Walton, S. D. O’Neal and F. G. Zalom. 2011. Drosophila suzukii (Diptera: Drosophilidae): invasive pest of ripening soft fruit expanding its geographic range and damage potential. J. Integr. Pest Manage. 2: 1Ð7. Received 13 June 2014; accepted 2 September 2014.