MEASUREMENT OF AIRBORNE PHEROMONE CONCENTRATIONS USING ELECTROANTENNOGRAMS - INTERACTIONS BETWEEN ENVIRONMENTAL VOLATILES AND PHEROMONE

Electroantennogram (EAG) measurements were carried out on the antennae of males of the lighthrown 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 re leased by the female and also to environmental volatiles present in th e air, The responses elicited by pheromone and environmental odours we re found not to be independent of each other, Pheromone responses were reduced by the presence of environmental odours compared to stimuli d elivered under filtered air conditions, This observation has implicati ons for attempts to use EAG equipment to measure pheromone concentrati ons in the air under field conditions, Until the exact nature of the i nteraction between the two stimuli is elucidated it will not be possib le to accurately measure absolute pheromone concentrations in the fiel d using this technique with these two species although comparative mea surements will still be possible, Simultaneous measurements on pairs o f insects, male and female of the same species or males of different s pecies, may offer a partial solution to this problem.