Sex pheromone blend discrimination by male moths fromE andZ strains of European corn borer

Sex pheromone behavioral responses were analyzed in a flight tunnel with European corn borer,Ostrinia nubilalis (Hübner), males from three distinct populations. Males from a bivoltine and a univoltine biotype using a 97.8∶2.2 blend (Z strains) of (Z)- and (E)-11-tetradecenyl acetate were assayed with treatments containing 0, 0.5, 1, and 3% of theE isomer. Males from neither population oriented in the plume to the 100%Z treatment, but bivoltine males oriented and flew to the source to the other three treatments, whereas univoltine males oriented and flew to the source only to the 1 % and 3 %E treatments. Males from a bivoltine biotype using a 1∶99 blend ofZ/E isomers (E strain) were assayed with sources containing 0, 0.5, 1, and 3% of theZ isomer. Males did not orient to the 0%Z source, but oriented and flew to the source to the other three treatments. In addition to using opposite geometric isomers for the main pheromone component, the bivoltineE strain differed from the bivoltineZ strain by producing and responding better to 1 % of the minor component and by storing 3 times more pheromone in the female glands. Contrary to previous reports, the blend of two pheromone components is significantly better than the main component alone in eliciting oriented flight and close-range behavior with males from all three populations of European corn borer.