Electrophysiological and behavioral responses of oriental fruit moth to the monoterpenoid citral alone and in combination with sex pheromone.

The monoterpenoid citral synergized the electroantennogram (EAG) response of male Grapholita molesta (Busck) antennae to its main pheromone compound Z8-12:OAc. The response to a 10-μg pheromone stimulus increased by 32, 45, 54, 71 and 94% with the addition of 0.1, 1, 10, 100 and 1,000 μg of citral, respectively. There was no detectable response to 0.1, 1, or 10 μg of citral; the response to 100 and 1,000 μg of citral was 31 and 79% of the response to 10 μg of Z8-12:OAc. In a flight tunnel, citral affected the mate-seeking behavior of males. There was a 66% reduction in the number of males orientating by flight to a virgin calling female when citral was emitted at 1,000 ng/min ≍1 cm downwind from a female. Pheromone and citral induced sensory adaptation in male antennae, but citral did not synergize the effect of pheromone. The exposure of antennae to 1 ng Z8-12:OAc/m(3) air, 1 ng citral/m3 air, 1 ng Z8-12:OAc + 1 ng citral/m3 air, or to 1 ng Z8-12:OAc + 100 ng citral/m3 air for 15 min resulted in a similar reduction in EAG response of 47-63%. The exposure of males to these same treatments for 15 min had no effect on their ability to orientate to a virgin calling female in a flight tunnel. The potential for using citral to control G. molesta by mating disruption is discussed.