Efficacy of Neonicotinoid Seed Treatments in Cotton on Thrips

EFFICACY OF NEONICOTINOID SEED TREATMENTS ON THRIPS IN COTTON Abstract Seed treatments are common and effective pest control methods in many crop systems. Cotton seed treatments are often used for control of early season pests. A market shift in seed treatments to neonicotinoid formulations followed the phasing out of aldicarb (Temikš). Imidacloprid and thiamethoxam (Cruiserš) are two commonly used insecticide cotton seed treatments, but concern lies with the possibility of varying degrees of efficacy of these seed treatments on the different thrips species. The common thrips species that infest cotton seedlings are tobacco thrips (Frankliniella fusca), flower thrips (Frankliniella tritici), western flower thrips (Frankliniella occidentalis), and onion thrips (Thrips tabaci), and each of these exhibit different degrees of susceptibility to various insecticide formulations. It is necessary for us to evaluate the thrips species composition in Texas cotton, as well as the impact of thiamethoxam and imidacloprid seed treatments on those species. The evaluated locations throughout Texas included: Chillicothe, College Station, Halfway, Kress, Lamesa, and Wall. These are representative sample areas of the High Plains, Rolling Plains, and Central Texas areas. Thrips populations were low in Chillicothe, Lamesa and Wall, but there were fewer thrips in treated seeds for most sampling dates in College Station, Halfway and Kress. Imidacloprid treated seed resulted in greater yield than the control in College Station, which was the only harvested location with thrips populations exceeding treatment threshold (one visible thrips per true leaf) levels. Greenhouse evaluations of thiamethoxam and imidacloprid seed treatments for western flower thrips provided information on maximum potential efficacy of these products in a more controlled environment.