Iris Yellow Spot and Thrips in Onions
Onion is an important crop in the U.S., generating over $900 million annually in farm receipts from 2005 to 2010. Western states cultivate 54,000 hectares (nearly 80% of all U.S. summer production) and produce a large portion of the world supply of onion seed. Onion thrips, an insect that feeds on onion plant leaves, is the most serious pest of onion worldwide. It has become an even greater threat as a vector of Iris yellow spot virus (IYSV), a devastating new onion disease. The projected economic impacts of IYSV and its insect vector in the U.S. total $60 to 90 million; increased pesticide use adds $7.5 to 12.5 million to pest control costs as well as environmental costs that are difficult to measure. Integrated Pest Management (IPM) strategies are needed to deal with these immediate and serious threats; however, much is still unknown about IYSV and thrips. Lacking knowledge and resources, growers in the western U.S. currently rely on insecticides for thrips management even though insecticide resistance problems have been reported for over 15 years. As pest populations and disease outbreaks spread rapidly around the world, scientists must develop IPM strategies that include pest-tolerant and disease-resistant onion varieties, biological control options, and modified farming practices in order to ensure economically and environmentally sustainable onion production.