Economic Threshold of Wheat Streak Mosaic Virus in the Texas High Plains

Wheat streak mosaic virus is among the most economically important viruses affecting winter wheat in the Great Plains region. Depending on infection severity, the virus can lead to significant yield loss, rendering continuation of mid-season input application uneconomical. Determining an economic threshold infection severity soon enough in the season so that farmers could discontinue input application, could increase farmer net returns and save resources. Using data from a field experiment involving 114 sample plots, which were sensed for the presence of the virus using reflectance readings, we conducted econometric and partial budget analysis to estimate the effect of the virus on yields, and determine the economic threshold level of infection. Results indicate varying threshold infection severity depending on the date of sensing, with earlier sensing having a higher threshold than sensing at a later date. Further, estimates show that the virus can reduce yields by as much as 35 percent for every unit increase in reflectance readings, between growth stages Feekes 5 and 6. Without a better predictor of yield losses, however, it is rarely going to be the case that it would pay to discontinue input application.