Putative Host Volatiles Used by Habrobracon hebetor (Hymenoptera: Braconidae) to Locate Larvae of Plodia interpunctella (Lepidoptera: Pyralidae)

Abstract

Indianmeal moth, Plodia interpunctella (Hubner) (Lepidoptera: Pyralidae), is a post-harvest pest of grains, milled and processed food, processing plants, warehouses and bakeries. The parasitoid, Habrobracon hebetor (Say) is among the most important natural enemies of Pyralidae infesting stored grains and grain products. Many parasitoids use semiochemicals originating from their hosts, or host’s habitat as cues to locate hosts, hosts’ food or habitat. The authors used Y-tube and four-way olfactometers to assay responses to stimuli with the moth host and thereby understand the role of host-associated semiochemicals in host location by H. hebetor. Responses of mated parasitoid females were assayed to the following stimuli: P. interpunctella sex pheromone, female adults, larvae, or hexane extracts of residue of the rearing medium. Generally, host-related odor sources generated stimuli that elicited better responses than those to blank controls. Previous exposure to odor sources from the host shortened latency periods and response times compared to naive females. Odors emanating from live moth larvae elicited the strongest responses. When responses from the four odor sources were compared in a four-way olfactometer, it was confirmed that volatiles from larval moths elicited the strongest attraction to the parasitoid. The involvement of host-specific chemical cues in both long and short range host location by female parasitoid is discussed.