A LONG-RANGE ATTRACTANT KAIROMONE FOR EGG PARASITOID TRISSOLCUS-BASALIS, ISOLATED FROM DEFENSIVE SECRETION OF ITS HOST, NEZARA-VIRIDULA

A short-chain alpha,beta-unsaturated aldehyde, (E)-2-decenal, present in the defensive metathoracic gland of Nezara viridula (L.) (Heteropte ra: Pentatomidae), stimulates a behavioral response in the egg parasit oid Trissolcus basalis (Woll.) (Hymenoptera: Scelionidae). Preliminary studies showed that T. basalis are attracted to an area containing ad ult N. viridula, but we also found that female T basalis would examine and probe glass beads coated with an acetone extract of the metathora cic gland from males or females. Using this bioassay, the kairomone wa s isolated by bioassay directed by preparative gas chromatography and identified by NMR and mass spectrometry as (E)-2-decenal. The biologic al activity of the identified aldehyde was compared with analogs to de termine specificity. An unstable Z isomer was found to be more active but not present in detectable or behaviorly relevant levels in the hos t, based on the bell-shaped dose-response curve of the two isomers. An investigation was also designed to determine if the E isomer was also responsible for the egg recognition kairomone activity previously rep orted. However, no 2-decenal isomers were detected in host egg extract s and the chemical characteristics of the 2-decenal isomers differ fro m the unidentified egg recognition kairomone. The role of the (E)-2-de cenal in attracting female T.