CHEMICAL ECOLOGY Response of Cranberry Weevil (Coleoptera: Curculionidae) to Host Plant Volatiles ZSOFIA SZENDREI,1,2 EDI MALO,1,3 LUKASZ STELINSKI,4 1 AND CESAR RODRIGUEZ-SAONA Environ. Entomol. 38(3): 861Ð869 (2009) ABSTRACT The oligophagous cranberry weevil, Anthonomus musculus Say, causes economic losses to blueberry growers in New Jersey because females deposit eggs into developing ßower buds and subsequent larval feeding damages buds, which fail to produce fruit. A cost-effective and reliable method is needed for monitoring this pest to correctly time insecticide applications. We studied the behavioral and antennal responses of adult A. musculus to its host plant volatiles to determine their potential for monitoring this pest. We evaluated A. musculus response to intact and damaged host plant parts, such as buds and ßowers in Y-tube bioassays. We also collected and identiÞed host plant volatiles from blueberry buds and open ßowers and performed electroan- tennograms with identiÞed compounds to determine the speciÞc chemicals eliciting antennal responses. Male weevils were more attracted to blueberry ßower buds and were repelled by conspeciÞc-damaged buds compared with clean air. In contrast, females were more attracted to open ßowers compared with ßower buds. Nineteen volatiles were identiÞed from blueberry buds; 10 of these were also emitted from blueberry ßowers. Four of the volatiles emitted from both blueberry buds and ßowers [hexanol, (Z)-3-hexenyl acetate, hexyl acetate, and (Z)-3-hexenyl butyrate] elicited strong antennal responses from A. musculus. Future laboratory and Þeld testing of the identiÞed compounds in combination with various trap designs is planned to develop a reliable monitoring trap for A. musculus. KEY WORDS highbush blueberry, Y-tube bioassay, headspace analysis, gas chromatography-mass spectrometry, electroantennogram In the process of host selection, arthropod pests may weevil [Otiorhynchus sulcatus (Fabricius)] respond use plant volatiles to locate hosts (Bruce et al. 2005 to host plant volatiles in behavioral bioassays (Bu- and references therein). Host plant volatiles are denberg et al. 1993, Wibe et al. 1997, van Tol and often used as attractants in traps, thus increasing Visser 2002). Previous studies by Mechaber (1992) monitoring and/or trap-and-kill efÞciency (Rodri- using a Y-tube olfactometer showed that adult A. guez-Saona and Stelinski 2009). The oligophagous musculus were attracted to damaged cranberry ßower bud feeding cranberry weevil (a.k.a. blossom (Vaccinium macrocarpon Ait.) ßower buds com- weevil, Anthonomus musculus Say, Coleoptera: Cur- pared with clean air or healthy plants. However, that culionidae) may use speciÞc volatile chemicals to single study to date did not test the behavioral locate a suitable host plant. Within the Curculion- response of A. musculus to other plant parts that also idae, i.e., the apple blossom weevil (A. pomorum L.), receive damage in the Þeld, such as leaf buds and the boll weevil (A. grandis Boheman), and the open ßowers. strawberry blossom weevil (A. rubi Herbst) respond Anthonomus musculus is native to North America electrophysiologically to host plant volatiles (Dick- and ranges from Ontario and New England south to ens et al. 1990, Kalinova´ et al. 2000, Bichao et al. Florida and west to the Rocky Mountains (Dittl 2005); and numerous species, i.e., the white pine 1988). This pest causes economic losses to commer- weevil [Pissodes strobi (Peck)], the banana weevil cial cranberry and blueberry growers in Massachu- (Cosmopolites sordidus Germar), and the black vine setts, New Jersey, Wisconsin, and Michigan. In early spring, eggs are deposited into developing ßower buds and subsequent larval feeding prevents the 1 Rutgers University, P.E. Marucci Center for Blueberry and Cran- berry Research and Extension, 125A Lake Oswego Rd., Chatsworth, development of fruit that causes signiÞcant eco- NJ 08019. nomic losses to commercial blueberry growers. The 2 Corresponding author, e-mail: [email protected]. immature stages are protected by the buds during 3 Current address: Departmento de Entomologõ´a, El Colegio de la their development; therefore, management strate- Frontera Sur, Tapachula, Chiapas CP 30700, Me´xico. 4 University of Florida, Citrus Research and Education Center, 700 gies typically target the mobile adults. Adults feed Experiment Station Rd., Lake Alfred, FL 33850. on the developing buds, ßowers, and leaves, and 0046-225X/09/0861Ð0869$04.00/0 ᭧ 2009 Entomological Society of America 862 ENVIRONMENTAL ENTOMOLOGY Vol. 38, no. 3 they are active during the day. Their peak activity observation under a stereomicroscope). Buds were is during the spring when buds and ßowers are detached from the branches as needed, immediately developing, but they can be found in blueberry before use in assays. Þelds throughout the growing season (Doehlert and Weevils were placed individually at the bottom of Tumlinson 1947; Z.S., personal observation). Adult the Y and were observed until a choice was made or weevils actively move around on plants on sunny for a maximum of 10 min. Thereafter, weevils were days and therefore can be monitored in highbush sexed based on characters of the pygidium (J. Prena, blueberries with beat trays. On cloudy days, visual personal communication). Weevils not making a assessment of blossom damage provides an alterna- choice within 10 min were recorded as nonrespond- tive monitoring technique. These techniques are ing; each individual was tested once. After each rep- labor intensive, unreliable, and inaccurate because licate, the position of the odor sources was random- of the patchy distribution of the pest. Furthermore, ized to exclude the possibility of positional bias. weevils tend to drop to the ground when scouts Treatment types were changed after every two rep- move plants while searching for them. A cost-effec- licate runs, and new odor sources were prepared every tive and reliable method is needed for monitoring 2Ð3 h. After each weevil and odor source treatment this pest and timing of insecticide applications. run, the glass tubes were Þrst rinsed with methanol To date, semiochemical attractants have not been and then with hexane and subsequently baked in a Њ identiÞed for A. musculus; therefore, the goal of this drying oven at 60 C for 15 min. Each experiment was study was to assess the responses of this species to replicated 17Ð26 times over a period of 7Ð12 d. All experiments were performed between 0900 and 1700 host plant volatiles and determine the possibility of Ϯ Њ their use in behavioral manipulation of this pest. hours at 21 2 C and 800Ð900 lux, under laboratory Our speciÞc objectives were to (1) evaluate the conditions. behavioral responses of adult A. musculus to intact Volatile Collection and Analysis. All plant material and insect-damaged host plant parts, such as buds for the volatile collections was obtained from mature and ßowers; (2) isolate and identify host plant vola- highbush blueberry plants (variety Duke) grown in an experimental Þeld in Chatsworth, NJ. Flower volatiles tiles from blueberry buds (A. musculus damaged and were collected using a push-pull system (Rodriguez- undamaged) and open ßowers; and (3) investigate Saona et al. 2001, 2006). Fresh, Þeld-collected antennal responses of weevils to individual volatile branches with Ϸ200 fully open ßowers were placed compounds to identify the speciÞc chemicals elic- inside a 4-liter volatile collection chamber (N ϭ 3; iting an antennal response. Analytical Research Systems). PuriÞed air entered through valves near the top of each chamber at 2 liters/min, and volatiles were collected in Alltech Su- Methods and Materials per-Q adsorbent traps (30 mg/trap; Analytical Re- search Systems) by pulling puriÞed air from the cham- Y-Tube Assays. Anthonomus musculus were col- bers at a rate of 1 liter/min. Bud volatiles were lected with beating trays in MarchÐApril 2008 from collected by placing 20 Þeld-collected ßower buds in two commercial highbush blueberry (Vaccinium a 10-ml glass vial (N ϭ 4). For the weevil-damaged corymbosum L. variety Duke) farms in central New buds, 10 Þeld-collected weevils were added to 20 Jersey. After returning them to the laboratory, weevils ßower buds in a 10-ml glass vial (N ϭ 8). Air was were maintained in environmental chambers (16:8 pushed in (1 liter/min) through a charcoal Þlter and Њ L:D, 15 C) in screen cages (30 by 30 by 30 cm) with out through a Super-Q trap. Volatiles were collected access to fresh buds and foliage ad libitum collected from 0900 to 1700 hours. daily from an unsprayed highbush blueberry Þeld (va- The collected volatiles from the Super-Q traps were riety Duke). eluted with dichloromethane (150 ␮l), and 400 ng of The olfactory preferences of A. musculus were n-octane (Sigma-Aldrich, St. Louis, MO) was added as tested using a Y-tube olfactometer (two 8-cm and an internal standard. Compounds were separated and one 12-cm arms; 2 cm diameter, ground glass joints; quantiÞed on a HewlettÐPackard 6890 Series gas chro- Analytical Research Systems, Gainesville, FL). Air matograph (GC), equipped with a ßame ionization was Þltered through activated charcoal and was split detector (FID) and an Agilent HP-1 column (10 m by into two 1 liter/min air streams. Subsequently, each 0.53 mm by 2.65 ␮m), and using He as the carrier gas air stream was delivered through glass tubes (14 cm (constant ßow ϭ 5 ml/min, velocity ϭ 39 cm/s). The long, 2 cm diameter) that held odor sources and that temperature program was 40ЊC for 1 min, 14ЊC/min to were connected to the olfactometer. Odor sources 180ЊC (2 min), and 40ЊC/min to 200ЊC, where it was from the plants consisted of 0.3Ð0.4 g of Þeld-col- maintained for 2 min. Individual compounds (ng/g of lected plant material (buds: leaf or ßower, damaged wet material/h) were quantiÞed based on compari- or undamaged; or fully opened ßowers).