The thrips complex associated with onion in Colorado
Mahaffey L, Cranshaw W, Schwartz H
Department of Bioagricultural Sciences and Pest Management Colorado State University, Ft. Collins, CO 80523.
Correspondence: linda.mahaffey@colostate.edu
Thrips problems affecting onions in Colorado have increased greatly in recent years because of: 1) difficulties in control due to development of insecticide resistance; and 2) emergence of thrips-vectored Iris yellow spot virus as a new disease of the crop. In response, a wide range of studies are being conducted at Colorado State University to better understand seasonal biology of thrips associated with onion and identifying effective pest management practices. Onion thrips, Thrips tabaci, is the predominant species in all production areas followed by western flower thrips, F. occidentalis and F.schultzei. Over 95% of all thrips are T. tabaci in most areas, but F. occidentalis was present in high percentage (ca. 24%) in southwestern Colorado. Introduction of thrips on transplants grown in California, Arizona and Texas is a significant source of thrips with 57% (8/14) and 95% (21/22) of samples infested in 2004 and 2005, respectively. Thrips tabaci predominated but other species present were F. ewarti, F. occidentalis, and Scirothrips longipennis. The ratio of Thrips tabaci to Frankliniella spp. did not shift in fields with repeated history of pyrethroid use (lambda-cyhalothrin).
