DEFINING INTERACTION BETWEEN ELECTROANTENNOGRAM RESPONSES OF EPIPHYAS-POSTVITTANA (LEPIDOPTERA, TORTRICIDAE) TO PHEROMONE AND OTHER VOLATILES

The potential for electroantennograms (EAGs) to assist in the measurem ent of atmospheric pheromone concentrations was examined in laboratory and field experiments by using multiple stimuli, the main component o f the pheromone of Epiphyas postvittana, (E)-11-tetradecenyl acetate, its Z-isomer (a behavioral antagonist), and alpha-terpineol (a represe ntative host-plant odor) were presented to the antenna simultaneously to simulate field conditions. The EAG results were compared with predi ctions from two models describing responses to combined stimuli, Respo nses are defined as log-additive if they can be described with the equ ation [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. Th e EAGs elicited by the added stimuli were inversely related to the con centration of the volatile in the background. EAGs elicited by all com bined stimuli followed the log-additive model, Our laboratory results were validated in field tests; alpha-terpineol represents the volatile s present in orchard air, In spite of this interaction between the per ception of pheromone and plant volatiles, the field EAG can be used fo r the measurement of atmospheric pheromone concentrations, where backg round odor concentrations are relatively constant. (C) 1997 Elsevier S cience Ltd. All rights reserved.