Developing the framework for a risk map for mite vectored viruses in wheat resulting from pre-harvest hail damage

Abstract:

Climate change is expected to adversely influence the weather and may increase the severity of meteorological events, including thunderstorms capable of producing crop damaging hail. Hail events occurring on pre-harvest wheat fields are known to be a significant contributor to outbreaks of virus diseases such as Wheat streak mosaic virus, Triticum mosaic virus , and Wheat mosaic virus, in the subsequent year. These viruses are vectored by the wheat curl mite (WCM) and volunteer wheat from pre-harvest hail events provides WCMs with a green bridge between harvest in the summer and planting in the fall. Controlling volunteer wheat through herbicide application and tillage has been shown to reduce WSMV transmission as long as it is conducted before emergence of the winter wheat crop. The goal of this study was to develop a risk product for WCM-vectored viruses based on pre-harvest hail damage. Traditionally, vegetation indices (VI; i.e. normalized difference vegetation index) are used to remotely identify hail damage in satellite imagery. However, during the highest risk period for volunteer wheat resulting from pre-harvest hail damage, the wheat crop is senescing and dramatically reducing its ‘greenness’, decreasing its sensitivity to changes in many VIs. Ground-based hyperspectral remote sensing over mechanically hailed sites indicates that reflectance from hailed wheat increases in the visible/near infrared spectrum. This information can be incorporated into a model using satellite imagery (LandSat and MODIS) and a 1 x 1 km resolution map of estimated maximal hail size produced by NOAA. The risk maps produced from these inputs will enable farmers and stakeholders to more effectively manage WCM-vectored viruses of wheat.