Date of this Version
McMechan A. J. 2016. Over-summering ecology of the wheat curl mite (Aceria tosichella Kiefer) Dissertation. University of Nebraska-Lincoln. 1-254.
The wheat-mite-virus complex is a consistent and significant threat to winter wheat production in the western Great Plains. This complex consists of three viruses (Wheat streak mosaic virus, Triticum mosaic virus, and Wheat mosaic virus that are transmitted by the wheat curl mite (Aceria tosichella Keifer). Yield impacts from this complex are typically associated with the presence of volunteer wheat that emerges prior to harvest as a result of hail occurring during the heading stages of wheat in early summer. Historical literature on pre-harvest germination has been primarily focused on accelerating breeding programs; however, critical gaps in knowledge exist on pre-harvest germination when evaluating risk for the wheat-mite-virus complex. A study was designed to evaluate pre-harvest germination potential of winter wheat by collecting heads at 7-9 day intervals beginning at the water-ripe stage until wheat harvest. In addition, risk categories were established based on the speed of germination because field germination will be limited by moisture availability. A second study was conducted in the field to evaluate the impact of environmental conditions on pre-harvest germination. Results indicate that risk for pre-harvest germination begins at the late milk stage with increasingly greater risk for germination up to harvest. In addition, risk for germination is highly dependent on available moisture following hail events. Historical observations, as well as anecdotal evidence indicate that other hosts besides wheat can support WCM during the over-summering period; however, the risk of these hosts to fall planted wheat is poorly understood. Greenhouse reproductive studies, a field study on mite movement and virus impact, and a weed survey were conducted to evaluate the risk potential of over-summering hosts. Results showed that barnyard grass is a high-risk over-summering host for the wheat-mite-virus complex; however, its frequency is relatively low across the central Great Plains. Green foxtail was comparatively a lower risk host, but it was found in higher frequencies in the weed survey. Foxtail millet, another summer annual, showed significant mite movement under field conditions; however, virus impact was minimal. In addition, greenhouse studies were a good predictor of field potential of all of the over-summering hosts with the exception of foxtail millet. The studies presented in this document provide critical information to better understanding the over-summering ecology and risk of the wheat-mite-virus complex.
Advisor: Gary L. Hein