MODIFICATION OF SEX-PHEROMONE BLEND DISCRIMINATION IN MALE ORIENTAL FRUIT MOTHS BY PREEXPOSURE TO (E)-8-DODECENYL ACETATE

A pre-exposure regime was developed to test the hypothesis that arrestment of in-flight behavior 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 percentage of Z8-12:OH at 2 dosages (3 and 100 .mu.g), males displayed an optimum number of completed flights of the source to the natural 6% E blend at 3 .mu.g, 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 behaviors in the sequence (landing and hair pencil display) requiring greater amounts of pre-exposure than early behavior (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.