Behavioral and electrophysiological responses of listronotus maculicollis (Coleoptera: Curculionidae) to volatiles from intact and mechanically damaged annual bluegrass

Listronotus maculicollis Kirby is a highly destructive pest of low mown, cool-season turfgrasses in the northeastern United States and Canada. Behavioral and electrophysiological assays were conducted to identify compounds that may be useful in developing novel monitoring techniques. In Y-tube assays, males and females responded differently to volatiles from intact and clipped annual bluegrass (Poa annua L.). Females were significantly attracted to intact P. annua but repelled from clippings; males did not respond significantly to either treatment. Electroantennogram (EAG) recordings from both sexes showed a significant response to volatiles from both treatments. Gas chromatography mass spectrometry (GC-MS) identified 12 volatile compounds from P. annua of which nine were common to both intact plants and clippings. On average, seven-fold higher quantities of volatiles were collected from clippings than from intact plants (24.3 versus 3.4 ng/g of tissue/h). Eight compounds were released in significantly greater quantities from clippings of which 50% were the n-C6 compounds hexanal, (E)-2-hexenal, and (Z)-3-hexenyl acetate, commonly referred to as "green leaf volatiles" (GLVs). Only octanal was emitted in greater amounts from intact plants than clippings. These nine compounds were tested individually against male and female antennae. Both sexes displayed greatest sensitivity to nonanal, octanal, and (E)-2-hexenal, but a significant doseresponse relationship was observed with all compounds tested. These studies indicate that both sexes respond physiologically and that L. maculicollis females exhibit behavioral responses to host-plant volatiles. Future studies will need to assess the effects of individual compounds and component mixtures on L. maculicollis behavior in the field.