Using a Degree Day Insect Development Model to Guide Strategic Management of Western Flower Thrips and Tomato Spotted Wilt Virus (Family Bunyaviridae, Genus Tospovirus) on Processing Tomato in the Central Valley of California

Tomato spotted wilt virus (TSWV) causes severe but sporadic losses in processing tomato production in California. The virus is transmitted by thrips, with the predominant vector species being the western flower thrips, Frankliniella occidentalis. Over the last five years a concerted research and outreach effort to develop and implement an integrated pest management (IPM) program has been associated with reductions in overall tomato spotted wilt disease (TSWD) incidence and the frequency of economic losses in commercial fields. In the last three years these measures have been supplemented with a temperature-driven degree day model, which projects the timing of thrips generation development events. The model is run on the USPEST. ORG servers in Corvallis, OR using weather information from five different locations in the Central Valley of California. The information is summarized weekly and provided to growers and professional crop advisors via a web page and RSS feed. We have used the system to target the second through fourth generations of thrips developing after winter. Data from three years of field observations indicate that this strategy, together with other measures, is successful in delaying TSWV infection sufficiently to prevent significant loss of quality or yield.