Host Plant Chemical Mediation of Heliothis Reproductive Behavior

Abstract

Phytophagous insects respond to chemicals from their host plants in a number of ways, including orientation or attraction in response to volatiles produced by plants. Orientation to odors from host plants may occur in order to locate food, mates, or oviposition sites. A detailed understanding of these behaviors are the chemical stimuli evoking them may provide useful means for attracting and trapping insect pests of crop plants. Heliothine moths (Helicoverpa and Heliothis herein) include a number of major pests of cultivated crop plants throughout the world. In North America, these include Heliothis virescens and Helicoverpa zea. In much of Eurasia (including Israel) Australia, and Africa, these include Helicoverpa armigera and Helicoverpa peltigera. These 4 species of concern all are attracted to odorants from host plants (Tingle and Mitchell 2992, Mitchell et al 1991, 1992 BARD feasibility study report). Host plant chemicals also play a role in the sexual behavior of Helicoverpa species. Synthesis and possibly release of sex pheromone in H. zea and H. phloxiphaga is stimulated by kairomones from hosts plants (Raina 1988, 1992). Pheromona scent marking on host plants also occurs in H. virescens and H. zea. Studies of several other insects, including the cabbage looper Trichoplusia ni, have a variety of other behaviors may occur in association with host plants, including the use of plants as sexual rendesvous sites and of direct involvement of plant chemicals in sexual behavior. Some pest species of moths also may use host plants as adult food sources. These studies were undertaken to develop a more thorough understanding of how Heliothis/Helicoverpa moths use host plant odorants to locate and select foods, mates, and oviposition sites. We used Heliothis virescens and Helicoverpa zea in Florida, and Helicoverpa armigera and Helicoverpa peltigera in Israel as objects of study because of their pest status. It is hoped that such an understanding will provide direction for work to discover and develop novel means to control these pests through behavioral manipulation. The specific objectives of the proposal were to 1) identify host odor affects on known Heliothine sexual behavior, 2) identify novel sexual behavior that is how dependent, 3) isolate and characterize host kairomones important to pest Heliothine host and mate-location behavior, and 4) investigate female attraction to males.