Monitoring Pickleworm (Lepidoptera: Pyralidae ...

HORTICULTURAL ENTOMOWCY

Monitoring Pickleworm (Lepidoptera: Pyralidae) Moths with Pheromone-Baited Traps D. MICHAEL

JACKSON, J. A. KLUN,l

A. P. KHRIMIAN,2

A. M. SIMMONS,

AND

K. A. SORENSEN3

U.S. Vegetable Laboratory, USDA-ARS, 2875 Savannah Highway, Charleston, SC 29414

J. Econ.Entomol.91(4): 950-956 (1998) ABSTRACT Populations of male moths of pickleworm, Diaphania nitidalis (Stoll), were monitored using 5 types of traps baited with virgin female moths and several formulations of sex pheromone lures. Modified box traps and wire-cone traps were highly effective when baited with either synthetic lures or virgin females. Unitraps baited with virgin females were less effective than box or wire-cone traps, and unitraps were ineffective when baited with synthetic pheromone lures. Nylon-cone traps were less effective than wire-cone or box traps. Pherocon sticky traps did not work with any lure.

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KEY WORDS

Diaphania nitidalis, trapping, pheromone lure, pest monitoring

P1CKLEwORM, Diaphania nitidalis (Stoll), is one of the more serious insect pests of Cucurbitaceae in the western hemisphere (York 1992). Female pickleworms deposit eggs in small clusters on leaves and flower buds of cucumber, Cucumis sativus L.; cantaloupe, Cucumis melo L.; pumpkin, Cucurbita pepo L.; squash, Cucurbita spp.; and other cucurbits. Fourth and 5th instars typically leave flowers and burrow into cucurbit fruits, rendering them unmarketable. This pest is especially destructive to pickling cucumbers because of the zero tolerance for infestations (York 1992). Growers often apply insecticides on a scheduled basis (typically, every 5 d) whether or not the pest is present. It is generally believed that pickleworms do not survive the winters in the Carolinas, but they do survive throughout the year in southern Florida (Reid and Cuthbert 1956, Pena et al. 1987). Wild cucurbits, especially Melothria pendula L., support pickleworm populations in Florida when cultivated hosts are not present (Elsey et al. 1985). Pickleworms gradually move northward during the spring and summer, often reaching major vegetable production areas in the southern Atlantic States in time to cause damage to cucurbit crops. Thus, there is a need for an effective monitoring system for pickleworm moths so that moth presence and population peaks can be predicted accurately and insecticide applications can be better timed.

This article reports the results of research only. Mention of a proplietary product does not constitute endorsement or a recommendationby USDAor by the North CarolinaAgriculturalResearch Servicefor its use. I InsectChemicalEcologyLaboratory,USDA-ARS, Beltsville,MD 20705. 2

Department of Chemistry,HowardUniversity,Washington,DC

20059. 3 DepartmentofEntomology,North CarolinaStateUniversity,Raleigh,NC 27695.

Klun et al. (1986) reported that a mixture of 5 components from the female-produced sex pheromone of the pickleworm was active in eliciting an upwind behavioral response from male moths indistinguishable from the response to mate-calling female moths. Elsey et al. (1989) demonstrated that rubber septa lures containing a blend of the 5 active pheromone components were effective in capturing male pickleworm moths in box traps. Elsey et al. (1991) then showed that modified box traps baited with a synthetic sex lure could be used to predict infestations of pickleworm larvae in cucumber fields. However, box traps are large, expensive, and impractical for use in a large-scale monitoring program for pickleworms. Valles et al. (1991) found that a smaller and less expensive green version of the bucket trap or unitrap (universal trap) baited with virgin females was more effective than box traps, Pherocon sticky traps, or nylon Heliothis traps. However, it is impractical to use live insects in any large-scale pest monitoring program. Thus, a small, effective inexpensive trap baited with a synthetic lure is needed for the development of an economical and manageable trap monitoring system for male pickleworm moths. In this study, we evaluated 5-component pheromone lures and virgin females in 5 types of traps for capture of male pickleworm moths.

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Materials

and Methods

Field experiments were conducted during 1995 and 1996 at the U.S. Vegetable Laboratory, Charleston, SC, and on a commercial vegetable farm (Planters Three) on Wadmalaw Island, Sc. All fields at the U.S. Vegetable Laboratory were planted with 'Early Prolific' yellow straight-neck summer squash, Cucurbita pepo L. At the Wadmalaw Island site, traps were placed in fields of cucumber, cantaloupe, pumpkin, and winter squash, Cucurbita maxima Duchesne. In 1995, some

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experiments (described below) were conducted inside a large screen cage (18.6 m wide, 44.2 m long, 2.7 m high) located at the U.S. Vegetable Laboratory. Seedlings of collard, Brassica oleracea L.; cantaloupe; and tomato, Lycopersicon esculentum Miller, were phmted in this cage for another experiment on silverleaf whiteflies, Bemisia argentifolii Bellows & Perring. However, the whitefly experiment did not interfere with the experiments described in this study. Five types of traps were evaluated as follows: (1) modified box trap (1 m3) (Elsey et al. 1989), (2) modified wire-cone Heliothis trap (75-50 cm) (Harstack et al. 1979,Johnson and McNeill 1994), (3) yellow and white unitrap (Universal Moth Trap, Pest Management Supply Company, Hadley, MA), (4) nylon lIeliothis trap (nylon-cone trap) (Ecogen, Scentry Division, Langhorne, PA), and (5) Pherocon lC sticky trap (Trece, Salinas, CAl. Seven lure treatments were evaluated in 1995.They were as follows: (1) virgin female pickleworm moths (2-3 d old); (2) Beltsville septa, a rubber septa treated with 818 ILgof the 5-component pickleworm pheromone (Klun et al. 1986); (3) WRM0755, a 5-component pheromone in a plastic laminate, constructed by Hereon Environmental Company (Emigsville, PAl; (4) WRM0765, a 5-component pheromone in a plasticcoated paper formulated by Hereon Environmental Company; (5) WRM0504, a 5-component plastic laminate formulated by Hereon Environmental Company in 1994that had been stored in a sealed package in the freezer at -18°C; (6) WRM0514, another 5-component plastic laminate formulated by Hereon Environmental Company in 1994 that had been stored in the freezer; and (7) unbaited traps. Only virgin females and WRM0755 were tested in 1996. Pickleworm Rearing. Pickleworms used for trapping studies were reared at the U.S. Vegetable Laboratory by methods modified from those of Elsey et al. (1984). Modifications included using a diet based on pinto bean, Phaseolus vulgaris L, (Burton 1969), the elimination of plastic louvers in the rearing crispers, lmd using layered instead of crumpled paper towels for pupation sites. The sexes of pickleworms were determined and separated as pupae. Emerged moths were fed a 10% honey solution and held in plastic emergence containers (Elsey et al. 1984) at ""15°C with a photoperiod of 14:10 (L:D) h for up to 5 d before use. Virgin female moths were removed from the cooler in the morning of an experiment and provided honey solution for several hours. Then 5 females were placed into each plastic-screen cylinder (15 em long, 2 em diameter). A water-wet cotton wick was pushed into the open end of the cylindrical screen chamber. Because natural pickleworm populations at the U. S, Vegetable Laboratory are often low, male moths (2-4 d old) from the laboratory colony were released daily into the field (see below), Males were removed from the cooler, fed honey solution until dusk, and randomly scattered over test fields, Male moths also were released daily into the screen cage in 1995. At Wadmalaw Island, only native populations of moths were monitored.

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Preparation of Pheromone Lures. The 5 compounds that make up the pickleworm sex pheromone were obtained as follows: (Z)-ll-hexadecenal and (Z)-ll-hexadecen-l-ol were purchased from Aldrich (Milwaukee, WI). (E)-ll-hexadecen-l-ol was prepared from (Z)-ll-hexadecenyl acetate (purchased from Aldrich) using an olefin inversion procedure (Sonnet and Oliver 1976). (Z)-ll-hexadecenyl acetate (10 g, 35,4 ILmol) was bromochlorinated by saturating a lOO-1L1 methylene chloride solution of the acetate with anhydrous HCl at -70°C followed by addition of N-bromosuccinimide (6,62 g, 37.2 ILmol). The mixture was stirred at -20°C for 3.5 h and processed as described by Sonnet and Oliver (1976). The bromochloride product (13.9 g mixture of regioisomers) was added to 130 g Nal in 650 ml dimethylformamide and heated for 23 h at 83°C. The reaction mixture was then processed as described by Sonnet and Oliver (1976) and distilled (120°C at 0,25 mm Hg) to yield 7,5 g (E)-ll-hexadecenyl acetate containing 4% cis isomer, This product was purified by argentation chromatography (25% AgN03 on silica gel [3060 ILm] eluted with 80:20hexane/ ethyl acetate) yielding pure trans isomer according to capillary gas chromatography (GC) (60 m by 0.25 mm DBWAX, J & W Scientific, Folsom, CA). The ester was hydrolyzed using 15% NaOH methanol to yield 6.3 g (E)ll-hexadecen-l-ol. The alcohol (0.9 g) was oxidized with pyridinium chlorochromate in the presence of sodium acetate (Corey and Suggs 1975) to yield 0,7 g (E)-ll-hexadecenal. (OE,Z)-1O,l2-hexadecadien-1-ol was prepared according to methods described by Bestmann et al, (1977) using 3,53 ILmol (E)- [12-tert-butyldimethylsilyloxy]-2-decanal and 3.88 ILmol butyltriphenylphosphonium bromide for the Wittig condensation. The resulting alcohol was purified using the urea-inclusion technique (Truscheit and Eiter 1962), yielding 400 mg 97%pure (OE,Z)-1O,l2-hexadecadien1-01. Oxidation (Corey and Suggs 1975) of 40 mg alcohol with pyridinium chlorochromate yielded 28 mg (0 E,Z) -1O,l2-hexadecadienal, A mixture of the 5 pheromonal compounds was prepared gravimetrically, Capillary gas chromatography analysis using the DBWAX column showed that the mixture had a chemical purity of97% and that the proportion of compounds was the same as the pickleworm pheromone described by Klun et al, (1986), An aliquot of neat compound was used to prepare a 81.8-lLgmixture per microliter of heptane solution. Rubber stoppers (5 by 9 mm septa) (Thomas Scientific, Swedesboro, NJ) were Soxhlet-extracted using 1:1 acetone/hexane and, after drying, individually treated with 10 ILl heptane solution of pheromone. The mixture (neat) was formulated by Hereon Environmental Corporation in 2 laminated pheromone dispensers having the following specifications. WRM0755 and WRM0504 dispensers were identical and were composed of polyvinylchloride polymeric permeable film (8 mil thick) with a mylar backing (non permeable), high-molecular-weight plasticizer, and 1 mg pheromone per 3.22 cm2 surface area.

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WRM0765 and WRM0514 dispensers were identical and were composed of a polyvinylchloride polymeric permeable film laminate (2 mil thick), low-molecularweight plasticizer, and 1 mg pheromone per 6.45 cm2 surface area. Both dispenser systems were designed to release pheromone at a low rate and a high rate, respectively. Pheromone lures were kept in a freezer (-18°C) until needed. Pheromone lures were held in the center of plastic screen cylinders (15 cm long, 2 cm diameter) with pins. These cylinders were attached to the traps with binder clips. Traps were monitored daily at the U. S. Vegetable Laboratory and 1-2 times a week at Wadmalaw. Pheromone lures were replaced in the field approximately every 2 wk. Screen-Cage Experiments, 1995.Four experiments were conducted inside the screen cage on day of year (DOY) 252-300 (9 September-27 October 1995). Ten feeding stations with honey-water (5%) were placed in the cage. For all experiments, 8 traps (4 wire-cone traps and 4 unitraps) were placed in 2 rows =10.5 m apart. Trap types were alternated, and they were positioned =7.5 m apart within rows. The cylindrical screen chambers containing virgin females or pheromone lures were attached near the center of the wirecone traps so that they projected slightly above the bottom plane of the outside cone and =46 cm above the ground. For the unitraps, the cylindrical screen chambers were supported vertically in the cone 2.5 cm above the cone apex as described by Valles et al. (1991). Virgin females were replaced daily. Lures were rotated daily so that each trap had a different lure each night. Male moths that had been captured were released back into the cage each day. Data from each experiment were analyzed by analysis of variance (ANOVA) using the SAS GLM procedure from the SAS System for Windows, version 6.12 (SAS Institute 1989,1993). Means were separated by Waller-Duncan K-ratio t-test (K = 100, a = 0.05) (Steel and Torrie 1960). For cage experiments 1-3, a single lure treatment versus virgin females was evaluated in 2 replications within the screen cage. The Beltsville septa was tested in cage experiment 1, where 275 male pickleworm moths were released into the cage. Traps were monitored over 4 consecutive nights (DOY 252-255). WRM0755 was tested in cage experiment 2, where 140 male pickleworm moths were released into the cage. Also, some moths from the previous experiment remained in the cage. Traps were monitored over 5 consecutive nights (DOY 256-260). WRM0765 was tested in cage experiment 3, where 100 male pickleworm moths were released into the screen cage. Traps were monitored over 5 consecutive nights (DOY 262-266). For Cage Experiment 4, 3 lure treatments (WRM0755, WRM0504, and WRM0514) and virgin females (5 moths per trap) were evaluated. In total, 750 male pickleworm moths were released into the screen cage. Also, some moths from previous experiments remained in the screen cage. The experiment was replicated over time. Traps were monitored for 14

ENTOMOLOCY

Vol. 91, no. 4

nights (DOY 275-278, 284-286, 291-293, and 297-300). Lures were changed on DOY 291. During the periods of DOY 279-283 and 294-296, temperatures were too low for experimentation, so lures were removed from the field and stored in a freezer at - 18°C.These same lures were returned to the cage on DOY 284 and DOY 297. U. S. Vegetable Laboratory Experiments, 1995.Two field experiments were conducted at the U. S. Vegetable Laboratory from 1 September to 13October 1995 (DOY 244-286). These experiments evaluated 5 lure treatments (un baited traps, 5 virgin females, Beltsville septa, WRM0755, and WRM0765) in 3 types of traps (box, wire-cone, unitraps). Both experiments used the same 5 lure treatments. Two sets of fresh pheromone lures were used for each experiment, and virgin females were replaced daily. Lures were rotated daily so that all traps had a different lure treatment each night. For the wire-cone traps, the plastic cylinders containing pheromone lures or virgin females were positioned in the center of the trap slightly above the bottom plane of the outer cone =46 cm above the ground. For the modified box traps, plastic cylinders were attached to a wooden stake inserted into the ground at the center of the trap. The cylinders were positioned so that they were even with the bottom plane of the box trap =30 cm from the ground as described by Elsey et al. (1991). All traps were positioned at least 30 m apart. For the 1st experiment, there were 3 replications of wire-cone traps, and there was a single replication of modified box traps for each lure treatment. The experiment was replicated over time with traps being checked and moths being removed daily for 8 consecutive nights (DOY 244-250). On DOY 250, the lures were changed, and the traps were checked on an additional 9 consecutive nights (DOY 251-261). Over the experimental period, 788 male pickleworm moths were released into the field. Moths were released along all Geld edges and down the center of the Geld. For the 2nd experiment, wire-cone traps and unitraps were evaluated in 2 replications for each of the 5 lures. Lures were rotated daily. Traps were initially monitored over 8 nights, but the evaluation period was split into 2 intervals (DOY 262-265 and 269-272) because of inclement weather. During the interim period (DOY 266-268), lures were stored in a freezer at -18°C. On DOY 275, new lures were added to each trap, and traps were monitored for another 7 nights (276-279 and 283-285). For this experiment, 348 male moths were released into the field. . Wadmalaw Island Experiment, 1995. This experiment determined the ef6.cacy of 3 pheromone lures (WRM0755, WRM0765, and Beltsville septa) in modiGed box traps. On 31 August 1995 (DOY 243), 6 box traps were placed into two 2-ha fields (pumpkin and squash) at the Wadmalaw site (3 traps per field). Pheromone lures were attached to a wooden stake inserted into the ground at the center of the trap as described above. Traps were checked, and captured moths were removed 10 times from DOY 245 to 305. Pheromone lures were changed 4 times (DOY 243, 254,271, and 289).

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ET AL.: PrCKLEWORM

u.s. Vegetable Laboratory Experiments, 1996. A sin~le field experiment was conducted at the U.S. Ve~etable Laboratory in 1996 to determine the trappin~ efficacy of 5 types of traps (modified box traps, wire-cone traps, unitraps, Pherocon lC sticky traps, and nylon Heliothis traps). This experiment was conducted from 17 July to 5 September 1996 (DOY 199248). There were 2 replications of traps, all of which were baited with WRM0755. Pheromone lures were positioned ""80 cm from the ground in wire-cone traps, nylon Heliothis traps, unitraps, and Pherocon lC sticky traps. Box traps were set up as in other experiments. Traps were checked and moths removed for a total of 18 nights (DOY 200-206, 235-242, and 244248). The pheromone lures were changed on DOY 235 and 244. In total, 788 moths were released. Wadmalaw Island Experiment, 1996. The relative trapping efficiencies of 4 types of traps (wire-cone, modified box traps, nylon Heliothis traps, and unitraps) were measured at the Wadmalaw Island site in 1996.Only the pheromone formulation WRM0755 was used in this experiment. Lures were changed approximately every 2 wk. All traps were located within rows of cucurbits and at least 25 m from the edge of a field. On 7 June 1996 (DOY 159), 4 box traps and 4 wirecone traps were set up in a randomized complete block design (4 replications) in 2 fields. Movement of the traps to new fields was required after the crop had been hmvested and destroyed. On 15 July (DaY 197), all traps were moved to 2 new fields. On 3 September (DaY 247), the traps were moved again to 2 new Relds. Four unitraps and 4 nylon Heliothis traps were added to the design on DOY 197 and were monitored ulltil26 September 1996 (DaY 270). The box traps and wire-cone traps were monitored until 28 October 1996 (DOY 302). The pheromone lures in the wire-cone traps, unitraps, and nylon Heliothis traps were placed ""'80 cm from the ground. Box traps were set up as before with the lures being ""30 cm above the ground. Over the season, the pheromone lures were changed 9 times. Results Screen-Cage Experiments, 1995. In cage experiments 1-3, few pickleworm moths were captured in unitraps baited with any of the synthetic pheromone lures (Table 1). However, virgin females were effective in unitraps. Virgin females were much more effective than the Beltsville septa in either trap type, but both Hercon formulations were as effective or more effective than virgin females in the wire-cone traps (Table 1). The unitraps also did not work with the commercial pheromone lures in cage experiment 4 (Fig. 1). It is not known why virgin females were not as effective in this experiment as they had been in cage experiments 1-3, but evening temperatures were lower than in previous experiments, which may have affected moth behavior. The newer pheromone lure (WRM0755) was more effective than either of the lures (WRM0504 and WRM0514) that had been stored in the freezer

PHEROMONE

953

TRAPPINC

Tahle 1. Daily captures of male pickIcworm moths in 2 trap designs baited with virgin female pickIeworm moths or 1 of 3 formulations of pickJeworm sex pheromone in n large screen ca~e at Charleston, SC, 1995

Lure treatment

Trap type

Vir!\in females Virgin females Beltsville septa Beltsville septa WRM0755 WRM0755 WRM0765 WRM0765

Wire-cone Unitrap Wire·cone Unitrap Wire-cone Unitrap Wire-cone Unitrap

Male pickleworm moths! trap! ni!,:ht" Exp 1

Exp 2

Exp 3

7.ooa 9.37a 2.38b 0.50c

2.70b 4.10b

3.30a 1.50b

9.40a O.40c 3.40a 0.20c

a Means in the same column followed by thc same letter are not significantly different accordin!\ to Waller-Duncan K-ratio t-test (K = 100, lJ< = 0.05) (SAS Institute 1989, 1993; Steel and Torrie 1960).

since the previous year, although these year-old lures were stilI moderately effective (Fig. 1). U.S. Vegetable Laboratory Experiments, 1995. In the 1st field experiment at Charleston in 1995,the box traps were more effective than wire-cone traps when baited with the synthetic lures (Fig. 2a). WRM0755 in box traps was more effective at catching male pickleworm moths than any other treatment. However, according to the ANOVA, there was no significant difference (F = 1.02; df = 3, 64; P = 0.39) in the number of moths captured in either box traps or wirecone traps baited with virgin females. For this experiment, WRM0755 was as effective as virgin females in the wire-cone traps (Fig. 2a). In the 2nd ReId experiment at Charleston in 1995, the wire-cone traps were more effective than unitraps when baited with the synthetic lures and with virgin

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Fig. 1. Mean number of male pickleworm moths captured in wire-cone traps and unitraps baited with vir~in females, fresh pheromone lures (WRM0755), or aged (WRM0504and WRM0514)pheromone lures in a lar~e screencageatthe U.S.VegetableLaboratory,Charleston,SC, 1995.Data bars followedby the same letter are not significantly different according to Waller-Duncan K-ratiot-test (K = 100, a = 0.05) (SASInstitute 1989,1993;Steel and Torrie 1960).Verticallinesindicatethe standarderror of the mean.

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JOURNAL

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Fig. 2. Mean number of male pickleworm moths captured in box traps (a), unitraps (b), and wire-conetraps (a and b) baited with virginfemales,1 of 3 pheromone lures,or unbaited traps in squash fieldsat the U.S.VegetableLaboratory,Charleston,SC,1995.Data barswithinan experiment followed by the same letter are not significantlydifferent according to Waller-Duncan K-ratio t-test (K = 100, a = 0.05) (SASInstitute 1989,1993;Steel and Torrie 1960).Vertical lines indicate the standard error of the mean. females (Fig. 2b). Only 2 moths were captured in unitraps baited with the Beltsville Septa, and neither WRM0755 nor WRM0765 captured any moths in unitraps. Both WRM0755 and WRM0765 were as effective as virgin females in wire-cone traps. Few moths were captured in unbaited traps in either field experiment at Charleston in 1995 (Fig. 2). Therefore, the unbaited trap treatment was not used in 1996. Wadmalaw Island Experiment, 1995. Pickleworm populations in both fields at the Wadmalaw Island site were high in 1995,and there was extensive damage by larvae, especially on pumpkins. Population peaks were observed in mid-September and mid-October. Modified box traps caught as many as 101 male pickleworm moths per trap per night when baited with WRM0755. This formulation captured nearly 3 times as many moths as the other formulations (Fig. 3). U.S. Vegetable Laboratory Experiments, 1996.The ANOVA for this experiment indicated that trap effects were highly significant (F = 8.89;df = 5,97; P < 0.001). Wire-cone traps were more effective than modified box traps (Fig. 4a). The nylon Heliothis traps caught fewer moths than either the box traps or wire-cone

Beltsville Sept.

Lure

Fig.3. Meannumber of malepicklewormmothscaptured in box traps baited with 1 of 3 pheromone lures on a commercialvegetablefarm on WadmalawIsland,SC,1995.Data barsfollowedby the sameletter are not significantlydifferent according to Waller-Duncan K-ratio t-test (K = 100, a = 0.05) (SASInstitute 1989,1993;Steel and Torrie 1960).Vertical lines indicate the standard error of the mean.

traps. Unitraps and Pherocon lC sticky traps were ineffective in this experiment (Fig. 4a). Wadmalaw Island Experiment, 1996. Pickleworm populations were high at the Wadmalaw Island site in 1996. In total, 3,426 moths were captured from DaY 159to 302 (1,495 trap-nights). Both modified box traps and wire-cone traps were effective in capturing 3 distinct population peaks (late June, late July, and mid-September) of male pickleworm moths (Fig. 5). No late population peak (mid-October) was observed in 1996in contrast to 1995.Over the entire season, trap captures amounted to 4.12:!: 0.93 (mean:!: SEM) male moths per trap per night in the box traps compared with 2.90 :!:0.84moths per trap per night in the wirecone traps. During the final population peak of 1996 (DaY 247-270),4 trap types were evaluated (Fig. 4b). For this experiment, the trap type in the ANOVA was highly significant (F= 7.45;df= 3,108; P< 0.001). Box traps averaged more male moths per night than any other trap type. The wire-cone traps also averaged higher trap captures than the nylon Heliothis traps or unitraps, which were ineffective (Fig. 4b). Discussion Modified box traps consistently captured more pickleworm moths than did the other trap designs. However, they are too large and too bulky to be of practical use in a large-scale pickleworm monitoring program. Unitraps are small, inexpensive, and easy to monitor, but were not effective when baited with any of the synthetic pheromone blends. Also, for some experiments, unitraps were less effective than other traps designs baited with virgin females. It also would be impractical to use virgin females for a large-scale monitoring program even if they were consistently effective in unitraps.

August 1998

JACKSON ET AL.: PICKLEWORM

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Fig. 4. Mean number of male pickleworm moths captured in 5 (a) or 4 (b) types of traps baited with WRM0755 pheromone lure at the U.S. Vegetable Laboratory, Charleston, SC (a) oron a commercial vegetable farm on Wadmalaw Island (b) ,1996. Data bars followed by the same letter are not significantly different according to Waller-Duncan K-ratio I-test (K

= 100, cr = 0.05)

(SAS Institute 1989, 1993; Steel and

Torrie 1960). Vertical lines indicate the standard error of the mean.

Our results were similar to those of Valles et aI. (1991) in that the commercially available nylon Heliothis traps were relatively ineffective, even after we moved the pheromone source above the bottom plane of the trap to improve trapping efficacy. On the other hand, the modified wire-cone traps used in our study were effective in capturing pickleworm moths, and were easier to use than box traps. For most experiments, wire-cone traps were slightly less effective than box traps. However, at certain times, including periods of low population levels, wire-traps were as effective as box traps (Figs. 4a and 5). Because we are most interested in monitoring male pickleworm moths at low population levels, wire-cone traps are the best option currently available. The 5-component lure, WRM0755, was the most effective pheromone evaluated in this study. It was superior or equal to virgin females in all experiments using wire-cone or box traps. This lure also was effective when aged in the freezer for >1 yr (WRM0504). Thus, WRM0755 shows great potential for use in monitoring pickleworm moths.

There may be several reasons why the synthetic pheromone lures were less effective than virgin females in the unitraps. Valles et aI. (1991) described male moths as landing on, and walking to, the bottom of the chambers holding the virgin females. Because these chambers were inserted into the funnel of the unitrap, males became trapped when they attempted to leave. We observed that male pickleworm moths approached, but did not land near the synthetic lures, and rarely flew into the unitraps. The 5-component lures used in our study lacked the 2 saturated compounds (hexadecanal and hexadecan-1-01) identified by Klun et aI. (1986). These minor components probably influence close-range behavior of the male moths. Klun et al. (1986) showed that, in £light tunnel experiments, male pickleworm moths spent more time at the pheromone source with the 7-component lure than they did with the 5-component lure lacking the saturated compounds. Further research should be conducted to determine if formulations of 7-component lures improve trap captures. A commercially available formulation of pickleworm pheromone would be valuable for a pickleworm monitoring program. A network of pickleworm traps along the East Coast would alert cucurbit growers in the mid-Atlantic states to impending pickleworm infestations. Growers then could begin their spray programs.

Acknowledgments We thank Sonny Hanckel for his excellent cooperation in letting us use his Wadmalaw Island farm, Planters Three. We thank J. A. Grob, ]. E. Cook, L. M. Cauthen, B. W. Davis, J. Graf, and B. K. Penny for their excellent technical assistance. We thank Hereon Environmental Company, Emigsville, PA, for providing some of the pheromone lures. This study was a cooperative investigation between USDA-ARS and the Department of Entomology at North Carolina State University.

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Received for publication

1998.

9 September 1997; accepted 13 May