Measurement of airborne pheromone concentrations using electroantennograms: Interactions between environmental volatiles and pheromone

Abstract

Electroantennogram (EAG) measurements were carried out on the antennae of males of the lightbrown apple moth, Epiphyas postvittana (Walker), and the codling moth, Cydia pomonella (L.), in an apple orchard. The antennae responded strongly to the major component of the pheromone released by the female and also to environmental volatiles present in the air. The responses elicited by pheromone and environmental odours were found not to be independent of each other. Pheromone responses were reduced by the presence of environmental odours compared to stimuli delivered under filtered air conditions. This observation has implications for attempts to use EAG equipment to measure pheromone concentrations in the air under field conditions. Until the exact nature of the interaction between the two stimuli is elucidated it will not be possible to accurately measure absolute pheromone concentrations in the field using this technique with these two species although comparative measurements will still be possible. Simultaneous measurements on pairs of insects, male and female of the same species or males of different species, may offer a partial solution to this problem.