Submitted to: Chemical Senses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 17, 2006
Publication Date: June 1, 2006
Citation: Zhang, A., Wang, S., Vitullo, J., Roda, A., Minnion, C., Bergh, C. 2006. Olfactory discrimination of sex pheromone stereoisomers: chirality recognition by pink hibiscus mealybug males. Chemical Senses. 31(7):621-626.
Interpretive Summary: The pink hibiscus mealybug is an invasive insect species that attacks more than 200 different plants and is a serious new threat to U.S. agriculture, forestry, and the nursery industry. If not controlled, it is estimated this exotic pest could cause $750 million of damage per year. Using a recently-identified chemical that is a sex attractant, we are able to answer several fundamental questions about biology and mate-finding mechanism of male mealybugs. The results from this study will be used by other scientists in conjunction with growers to develop cost-effective pest management strategies aimed at controlling the pink hibiscus mealybug.
Our previous field studies suggested that the two chiral centers that existed in sex pheromone of pink hibiscus mealybug, Maconellicoccus hirsutus, could elicit different male attractive responses. The chiral center in the acidic moiety of the ester seemed to be more critical than the alcoholic portion of pheromone molecule for attractiveness. The objective of the current study was to test this hypothesis by using stereoisomeric blends and pheromone-baited traps. Trap captures of male M. hirsutus showed that the pheromone with natural occurring (R)-maconelliyl (S)-2-methybutanoate and (R)-lavandulyl (S)-2-methylbutanoate [R-S configuration] was the most attractive blend and pheromone with unnatural S-S configuration was less attractive blend. The RS-R blend (containing R-R and S-R stereoisomers) did not cause capture of any male M. hirsutus equivalent to blank control and inhibitory effect was observed when R-R and S-R were combined with natural occurring R-S blend. These trap catch results observed from M. hirsutus represent an unique chirality recognition mechanism: olfactory discrimination against different stereoisomers depends on both asymmetric centers, it is essential with S-configuration for attraction and with R-configuration for inhibition on the acidic moiety, but the attractiveness shows some degree of tolerance towards chirality change in alcoholic portion of the pheromone molecules.