AGGREGATION PHEROMONES IN DRYOCOETES AFFABER (MANN) (COLEOPTERA, SCOLYTIDAE) - STEREOISOMERISM AND SPECIES-SPECIFICITY

Chemical analysis of whole body extracts and volatiles produced by fee ding males Dryocoetes affaber (Mann.) disclosed (+)-exo-brevicomin and (+)-endo-brevicomin [(+)EXOB and (+)ENDOB], as the major insect-produ ced potential pheromones. Laboratory bioassays and field-trapping expe riments demonstrated that (+)ENDOB is the main pheromone component, an d (-)ENDOB has an inhibiting effect. EXOB either as (+) or (+) appears to be a multifunctional pheromone. It has a synergistic effect in ble nds of EXOB and ENDOB in ratios up to 1:1, and it is inhibitory at hig her ratios. (-)EXOB was inactive. The most attractive blend for D. aff aber was a 1:2 blend of (C)EXOB and (+)ENDOB. When this blend was comp ared with a 9:1 blend, the best known blend for Dryocoetes confusus Sw aine, the responses by beetles of each of the two species were highly specific, providing evidence for pheromonal exclusion between the two congenerics. We conclude that the combined effect of chirality and the ratio of geometrical isomers of brevicomin determines both the level of response and the species-specificity of the chemical signal in D. a ffaber.