Decadienoates: Sex pheromone components of nettle caterpillars Darna trimaand D-bradleyi

This study was undertaken to identify sex pheromone components of nettle ca terpillars Darna trima and Darna bradleyi (Lepidoptera: Limacodidae) whose larvae defoliate oil palm, Elaeis guineensis, in southeast Asia. Coupled ga s chromatographic-electroantennographic detection (GC-EAD) analyses of pher omone gland extracts revealed two antennally active compounds produced by f emale D. trima and two by female D. bradleyi. Molecular structures of these candidate pheromone components were identified by electron-impact and chem ical-ionization mass spectrometry; retention-index calculations on DB-5, DB -23, and DB-210 columns; microanalytical treatments, as well as syntheses o f "auxilliary" compounds that facilitated identification of the compounds. The compounds from D. trima were 2-methylbutyl (E)-7,9-decadienoate (A) and (E)-2-hexenyl (E)-7,9-decadienoate (B); from D. bradleyi we identified met hyl (E)-7,9-decadienoate (C), and isobutyl (E)-7,9-decadienoate (D). In fie ld experiments in Malaysia, (S)-2-methylbutyl (E)-7,9-decadienoate (SA) in combination with B proved to be essential and synergistic pheromone compone nts for attraction of male D. trima. (R)-2-Methylbutyl (E)-7,9-decadienoate (RA) had no behavioral activity. Compound D singly attracted male D. bradl eyi, but addition of C to D at a 1:10 ratio significantly enhanced attracti veness of the bait. Synthetic pheromone blends were more effective trap bai ts than unmated female moths and could be developed for monitoring populati ons of D. trima and D. bradleyi in Asian oil palm plantations.