Modification of sex pheromone blend discrimination in male Oriental fruit moths by pre-exposure to (E)-8-dodecenyl acetate

ABSTRACT. A pre-exposure regime was developed to test the hypothesis that arrestment of in-flight behaviour in Oriental fruit moths, Grapholitha molesta (Busck), to high dosage and/or high %( E )-8-dodecenyl acetate blends was due to a high proportion of E8-12: Ac in the pheromone blend. When tested in a sustained-flight tunnel to various ratios of ( Z )- and ( E )-8-dodecenyl acetate plus a constant % of Z8-12: OH at two dosages (3 and 100μg), males displayed an optimum number of completed flights to the source to the natural 6% E blend at 3 μg, with significant decreases in response levels occurring to high % E blends at both dosages. Pre-exposure of males to E8-12: Ac alone enhanced their response at each dosage to selected higher % E blends that normally elicited low numbers of completed flights. Pre-exposure enhanced all aspects of the flight response, but this was dependent on both dosage and duration of pre-exposure, with later behaviours in the sequence (landing and hairpencil display) requiring greater amounts of pre-exposure than early behaviour (taking flight). Pre-exposure did not affect high response levels to optimal blends or low response levels to the highest or lowest blends tested at each dosage. The selective nature of the pre-exposure effect implied alteration of central processes in discrimination of blend rather than disturbance of olfactory receptor function.