Monitoring thrips populations and soybean vein necrosis virus (SVNV) in Wisconsin soybean

Soybean Vein Necrosis Virus (SVNV) was discovered in the southern United States in 2008 and has since been detected throughout the country’s major soybean growing regions, including Wisconsin. The only confirmed vector for this Tospovirus is the soybean thrips, Neohydatothrips variabilis (Beach). Because very little is known about SVNV, this study was set up to establish a better understanding of the epidemiology and economic impact of both the virus and thrips vector on soybean. Research objectives include monitoring thrips movements and changes in population composition in Wisconsin, identifying resistant soybean varieties, and determining the impact of the pathogen on yield. To accomplish these objectives, thrips flights were monitored via yellow sticky card traps at multiple soybean variety trials. Total thrips captures were estimated by subsampling the traps; to date eastern flower thrips, Frankliniella tritici (Fitch), appear to be the predominate species. The first year of the field study revealed two major flights of thrips into Wisconsin soybean fields, the first of which occurred during mid-July and the second between late August and early September. A yield and seed quality study was conducted on a soybean breeding line trial. Regression analysis showed a slight increase in the number of non-developed seeds per pod as disease severity increased.  There was little effect of SVNV on yield in this study. A future objective of this project is to find an efficient means of inoculation under laboratory conditions. Laboratory infectivity studies would facilitate investigating how timing of virus infection impacts yield and cultivar resistance screening.