Bisabolene epoxides in sex pheromone innezara viridula (L.) (Heteroptera: Pentatomidae): Role ofcis isomer and relation to specificity of pheromone.

Thetrans- andcis-(Z)-α-bisabolene epoxides (trans- andcis-(Z)-αBE) are the main components of the male sex pheromone inNezara viridula. The role of thecis isomer and the importance of thecis/trans proportion for the activity and the specificity of the pheromone are not clearly elucidated and were studied here. Interindividual variation of thecis/trans proportion produced by males was studied by individual hexanic extracts in two strains originating from the south of France (SF) and French West Indies (FWI). Thetrans isomer composed 42-82% of bisabolene epoxides in SF males and 74-94% of bisabolene epoxides in FWI males. Means (± SD) significantly differ between SF (62.8%±8.4) and FWI (82.4%±5.9) males in spite of this interindividual variation. Different isomers of bisabolene epoxide were synthesized and their EAG activity on female antennae was compared. Racemictrans- andcis-(Z)-αBE elicited low EAGs, not different from the nonnaturaltrans andcis (E)-αBE that were inactive on behavior. Behavioral tests revealed that racemictrans- andcis-(Z)-αBE attracted 45% (P<0.05) and 25% (P<0.05) of females, respectively. The same levels of attraction were obtained with (-) enantiomers oftrans- andcis-(Z)-αBE, which attracted 40% (P<0.05) and 20% (P>0.05) of the females, respectively. Binary blends containing 75/25, 50/50, and 25/75 proportions ofcis/trans isomers were more attractive thantrans-(Z)-αBE alone and response of females to the 25%cis/75%trans blend was significantly more important than the response totrans-isomer alone (P<0.05). The importance of thecis/trans proportion in relation with the specificity of the male pheromone is discussed.