Differences in the relationship between sensory adaptation of antennae and concentration of aerial pheromone in the oriental fruit moth and obliquebanded leafroller (Lepidoptera: Tortricidae): implications for the role of adaptation in sex pheromone-mediated mating disruption of these species.

The antennae of Grapholita molesta (Busck) are more susceptible to sex pheromone-induced sensory adaptation than the antennae of Choristoneura rosaceana (Harris). Adaptation is detectable in G. molesta at 1/1,000th the aerial concentration of pheromone (i.e., 5.0 x 10(-7) ng Z8-12:OAc/ml air) that is required to induce detectable adaptation in C. rosaceana (i.e., 5.0 x 10(-4) ng Z11-14:OAc/ml air). In addition, the predicted concentration of pheromone required to induce 50% adaptation in G. molesta (i.e., 1.2 x 10(-3) ng Z8-12:OAc/ml air) after 15 min of exposure is only one sixth the estimated aerial concentration required to induce the same level of adaptation in C. rosaceana (i.e., 7.5 x 10(-3) ng Z11-14:OAc/ml air) after 15 min of exposure. Sixteen percent and 28% adaptation of G. molesta antennae is predicted after 15 and 30 min of exposure to the equivalent of 1 ng Z8-12:OAc/m(3) air (i.e., 1 x 10(-6) ng Z8-12:OAc/ml air). The predicted level of adaptation in C. rosaceana antennae, however, is only 1.5 and 9.9% after 15 and 30 min of exposure, respectively, to the equivalent of 1 ng Z11-14:OAc/m(3) air (i.e., 1 x 10(-6) ng Z11-14:OAc/ml air). The approximately three-fold greater level of sensory adaptation in G. molesta antennae after 30 min of exposure to a pheromone concentration measured in pheromone-treated orchards (i.e., 1 ng/m(3)) may be one reason why this species is more readily controlled than C. rosaceana using mating disruption.