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CORESTA Meeting, Agronomy/Phytopathology, Rovinj, 2009, AP 02

Impact of tomato spotted wilt virus on tobacco production in Georgia

BERTRAND P.F.; MOORE J.M.
University of Georgia, Tifton, GA, USA

Spotted wilt, caused by Tomato Spotted Wilt Virus (TSWV), was first found in Georgia tobacco in 1986. Spotted wilt was probably introduced to Georgia plant communities by Western flower thrips ( Frankliniella occidentalis ) which were discovered in Georgia for the first time in 1983 - 1984 in flowers of peach and nectarine trees. By 1994 the disease was present in all tobacco producing counties causing occasional significant loss. Beginning in 1995 and continuing to present spotted wilt has been the greatest cause of disease loss, annually averaging 22% plant loss and 8% yield loss. There are three basic aspects of our physical and biological environment that seem to make this possible. a. The mild, somewhat wet climate greatly facilitates year around activity of a wide array of weeds and insects including thrips. b. TSWV has a very wide host range including several dozen weeds native to Georgia. Typically there are a dozen or more of these weeds actively growing in all months of the year. c. Two of the most important thrips vectors of TSWV and Frankliniella fusca which is native to and very abundant in Georgia and F. occidentalis which has become adapted and abundant as well. Both species can be found in some quantity in all months of the year. Spotted wilt has thus far proven impossible to predict from year to year. Transplant date trials have found temporal development of spotted wilt is largely random among locations. This may partially account for the non predictability of disease severity. Spotted wilt management programs are partial at best. A dual program of acibenzolar-s-methyl and imidacloprid applied in the seed beds prior to transplanting can give a 50% reduction in disease.