STERILITY Current research and goals: Current research involves using irradiation to sterilize tarnished plant bugs (Lygus lineolaris) and their progeny and determining the potential of the sterile bugs to suppress native populations. Essential to this study is quantifying the relative attractiveness of sterile females and the responsiveness of sterile males versus that of native bugs, which leads us into the area of olfactometers, traps, and pheromones. Additionally, we are determining the percentage of tarnished plant bugs that may be expected to enter diapause at any given time of the year and to develop a diapause model for this insect. We hope to be able to release sterile tarnished plant bugs into the limited areas where native populations are developing on their pre-cotton host plants and suppress the native populations to levels that will not be economically damaging. Knowing when tarnished plant bug populations enter and break diapause and developing a temperature-based model predicting the length of time required for bugs to adequately prepare for overwinterning will give us the ability to decide how to most efficiently apply insecticides. Results: We have determined the range of radiation dosages (100 to 200 Gy) that will produce a high degree of sterility in irradiated tarnished plant bugs or their progeny. This range is considerably higher than that determined for a closely related species (L. hesperus). Neither sperm production nor mortality seemed to be terminally affected by the dosages required to produce adequate sterility. The onset of significant percentages of diapausing bugs (50%) is triggered in tarnished plant bug nymphs hatching in late August, reaches near 100% by early September and remains there until mid March when it drops to near 50&. Between March and September, most bugs are reproductive. Future research: Future research will involve the quantification of the effectiveness of sterile bugs, the search for more efficient olfactometers and traps, especially traps that do not require the use of sticky material to capture bugs, and ventures into pheromone production. The development of a diapause model will require measurements of the amount of time required for tarnished plant bugs to develop the diapause syndrome over a series of temperatures. For more information contact: Eric Villavaso PO Box 5367 Mississippi State, MS 39762-5367 662-320-7468 evillavaso@ars.usda.gov Relevant Publications: Villavaso, E. J., and G. L. Snodgrass. 2003. Incidence of diapause in tarnished plant but, Lygus lineolaris (Palisot de Beauvois), in dynamic-photoperiod environmental cabinets. In Proc. Beltwide Cotton Conf. www.cotton.org/beltwide