Duration and location of attraction to herbivore-damaged plants in the tachinid parasitoid Exorista japonica

抄録

Odors from corn plants infested with the larvae of the noctuid herbivore Mythimna separata attract tachinid fly, Exorista japonica, females. We investigated the effects of elapsed time on the attraction of E. japonica to plants after host larvae were removed. The behavior of the flies within 5 min from introduction was observed in a wind tunnel. The percentage of flies attracted to the plants remained high (70%) for 5 h and decreased gradually after 24 h. The percentage of flies attracted to continuously damaged plants remained high for 5 days. In contrast, the percentage of flies reaching artificially damaged corn plants was high (85%) when tested soon after damage but decreased to 40% 1 h after damage. We also examined whether undamaged leaves from a damaged plant attracted tachinid flies. Undamaged leaves were not attractive when all other leaves on the same plant were damaged, even if damaged for several hours. In addition, the undamaged part of damaged leaves was not attractive. These results indicate that volatiles that attract E. japonica are only released from the damaged parts of leaves and these volatiles gradually decrease as the damaged plant ages.