Olfactory Responses of <Emphasis Type="Italic">Anaphes iole</Emphasis> (Hymenoptera: Mymaridae) to Volatile Signals Derived from Host Habitats

Anaphes iole Girault is a frequent parasitoid of Lygus spp. eggs in the United States, and has potential as a biological control agent against Lygus hesperus Knight in different crops. Feeding and oviposition by L. hesperus induce emission of plant volatiles, but studies to date do not address the role of plant volatiles in the host-searching behavior of A. iole. In this study, a four-arm olfactometer was used to test the responses of female parasitoids to odors emanating from cotton (Gossypium hirsutum L., Malvaceae) plants damaged by L. hesperus females, L. hesperus males, larvae of the nonhost Spodoptera exigua Hubner, or mechanically, or to odors from L. hesperus females alone. In addition, various plants damaged by L. hesperus females were evaluated in the olfactometer: cotton, alfalfa (Medicago sativa L., Fabaceae), common groundsel (Senecio vulgaris L., Asteraceae), annual ragweed (Ambrosia artemisifolia L., Asteraceae), and redroot pigweed (Amaranthus retroflexus L., Amaranthaceae). In all olfactometry bioassays, treatment odors were compared against three controls (humidified air). Results showed that A. iole females were consistently attracted to odors derived from different plant–L. hesperus complexes, while odors from plants subjected to nonhost (S. exigua) or mechanical damage and L. hesperus females alone were not attractive or only variably attractive. These findings suggest that while searching for hosts A. iole females use specific volatiles induced by L. hesperus feeding and oviposition to locate hosts inhabiting a wide variety of plants, including annual and perennial species from four plant families. It was suggested that future research should seek to identify the chemical elicitors involved in the release of plant volatiles attractive to A. iole females.