Plant Volatiles Mediate Host-Finding Behavior of the Apple Leafcurling Midge

The behavioral responses of apple leafcurling midge,Dasineura mali Kieffer, mated females to foliage from host and nonhost trees were investigated in a wind tunnel. When released downwind of apple or pear foliage, females exposed to apple were more likely to exhibit upwind flight and to approach and land on foliage. On apple foliage, landings were concentrated on buds and immature leaves. Probability of taking flight and latency to flight did not differ for females exposed to apple and pear. When foliage was placed behind screens to obscure plant visual stimuli, females again distinguished between apple and pear, with more of the females exposed to apple odors flying upwind and landing. Females exposed to pear odors were more likely to fly upwind, approach, and land than females exposed to clean air. Odors from immature apple foliage triggered orientation responses in a larger percentage of females than odors from mature apple foliage. A dichloromethane extract of immature apple foliage also triggered orientation responses.