BIOLOGY AND MANAGEMENT OF IRIS YELLOW SPOT VIRUS (IYSV) AND THRIPS IN ONIONS

Onion (Allium cepa) is an economically important crop in the U.S., generating over 900 million dollars annually in farm receipts from 2000 to 2004. U.S. onion production area ranges from 65,000 to 70,000 hectares annually, with over 80 percent of the summer production in the western states. On average, 53 million metric tons of onion bulbs are harvested annually from nearly 3 million hectares worldwide. A significant portion of the U.S. and world supply of onion seed is produced in the western U.S., primarily in the Pacific Northwest. Projected economic impacts of Iris yellow spot virus and thrips in the U.S. could reach 60 million dollars (10 percent loss) to 90 million dollars (15 percent loss), in addition to environmental and economic costs due to additional pesticide sprays for thrips control (7.5 to 12.5 million dollars for 3 to 5 additional sprays on 48,500 hectares per year) on onion, and potentially on other allium crops.Iris yellow spot virus and its Thrips tabaci vector represent an immediate and serious threat to sustainable and productive onion production in the U.S., and the recent detection of this disease in numerous onion producing countries worldwide emphasizes the need to develop economically sound and effective IPM strategies. The objectives of this project are to 1) Screen onion germplasm for improved levels of tolerance to IYSV and thrips; 2) Study the biology and epidemiology of IYSV and thrips, and impacts of chemical, cultural and biological tactics that can reduce their impacts upon onions; and 3) transfer information on progress dealing with IYSV and thrips biology and IPM strategies to the onion industry and other interested parties. The outcome is the development of high yielding onion cultivars with increased tolerance to IYSV and/or thrips will be incorporated into commercial production and that this will lead to reduced pesticide use for managing thrips resulting in savings to the producer and positively impacting the environment.