Defining Interaction between Electroantennogram Responses of Epiphyas postvittana (lepidoptera: Tortricidae) to Pheromone and Other Volatiles

Abstract

The potential for electroantennograms (EAGs) to assist in the measurement of atmospheric pheromone concentrations was examined in laboratory and field experiments by using multiple stimuli, the main component of the pheromone of Epiphyas postvittana, ( E)-11-tetradecenyl acetate, its Z-isomer (a behavioral antagonist), and α-terpineol (a representative host-plant odor) were presented to the antenna simultaneously to simulate field conditions. The EAG results were compared with predictions from two models describing responses to combined stimuli. Responses are defined as log-additive if they can be described with the equation [EAG (total) =a (log ([P x]+[B y])+c] and as linear–additive if the EAG follows the equation [EAG (total) =a (log [P x])+c+a′(log [B y])+c′] where [B y] is the concentration of the stimulant background odor and [P x] is the concentration of an additional odor stimulus. The EAGs elicited by the added stimuli were inversely related to the concentration of the volatile in the background. EAGs elicited by all combined stimuli followed the log–additive model. Our laboratory results were validated in field tests; α-terpineol represents the volatiles present in orchard air. In spite of this interaction between the perception of pheromone and plant volatiles, the field EAG can be used for the measurement of atmospheric pheromone concentrations, where background odor concentrations are relatively constant.