Electrophysiological and behavioral studies to test attractants semiochemicals for Stegobium paniceum L. (Coleoptera: Anobiidae)

Stegobium paniceum (L.) (Coleoptera: Anobiidae), the drugstore beetle, is one of the major pests for a wide variety of dry and durable stored agricultural products. Females of S. paniceum produce a sex pheromone, (2S,3R,1'R)-Stegobinone, that attracts males. Nevertheless, trapping experiments using the synthetic sex pheromone in many cases showed low levels of captures, perhaps because of isomerization of the pheromone compound in ambient conditions. To date, very few brands of commercially S. paniceum pheromone are available in the market. In this study, we evaluated in electrophysiological (EAG) and behavioral bioassays (two-choice olfactometer), the response of S. paniceum male and female to racemic mixtures of the sexual pheromone and its isomers. In particular were tested: 1) racemate A, (2S,3R,1'R)-Stegobinone plus the form 2R,3S,1'S; 2) racemate B, (2R,3S,1'S)-Stegobinone plus the form 2R,3S,1'R. The racemates were tested alone or in combination. Furthermore, a headspace collection of the colony (insects and substrate) was tested in olfactometer as candidate attractant to improve trap captures. EAG results showed that both racemic mixtures tested elicit dose-dependent responses in males but not in females. Olfactometer bioassays evidenced attraction response of males to racemate A tested alone or in combination with B. However, the racemate B alone elicited repellency in both sexes. Finally, the colony headspace extract elicited attraction in both sexes of S. paniceum.