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

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.