Window of risk for volunteer wheat establishment and wheat curl mite (Aceria tosichella K.) infestation

Wheat is an important food grain worldwide, and it is the primary dryland crop within the western Great Plains. The wheat-mite-virus complex is the largest cause of disease loss in winter wheat production in the western Great Plains. This complex consists of three viruses, Wheat streak mosaic, Wheat mosaic, and Triticum mosaic viruses. All of these viruses are transmitted by the wheat curl mite.  Widespread outbreaks of this complex are most often linked to pre-harvest volunteer wheat resulting from hail. A study was conducted to determine the stages of wheat head development that can result in wheat germination, volunteer wheat establishment and infestation by wheat curl mites as a result of hail. Wheat heads were collected from four varieties (Camelot, Mace, Millennium, and Pronghorn) at two separate locations during the summer of 2012. Heads were collected every five to seven days during head development. Each wheat head was staged, and placed on sterilized greenhouse soil in separate containers. Wheat heads were rated 21 days later for germination, plant height, and mite presence. Results indicate that wheat can germinate as early as the early milk stage. Both wheat variety and developmental stage impacted total germination and the time required for germination. In late stage wheat, some mites were able to survive until germination and establish on the new seedlings. The results from this study will provide an estimation of the window of risk for the development of pre-harvest volunteer winter wheat and the subsequent risk for mite infestation of that volunteer.