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The objectives of this project are 3-fold. First, we wish to determine how crop stresses including weeds, viruses, and soil moisture alter wheat/weed competitive interactions. Secondly, we wish to develop the data needed to assess the threat of weed biotypes and wheat varieties as sources of wheat viruses throughout the Great Plains. Thirdly, we will distribute our results through our extension responsibilities and advance a regional effort to mitigate the threat of wheat viruses to our cropping system. <P>The long-term goal of this project is to provide joint weed control and virus management recommendations for small grain growers throughout the Great Plains and PNW. We will achieve this goal by assessing the interrelationships between crop stress including soil moisture, viruses, and weeds on achievable wheat yields. <P>We will investigate solutions to preventing virus epidemics by evaluating the susceptibility of crop varieties and weed biotypes to virus infection by wheat viruses including Wheat streak mosaic virus (WSMV), High Plains virus (HPV), and a newly identified virus, Triticum mosaic virus (TriMV).<P> Educational efforts will be integral to the success of this proposal in changing crop management practices throughout the Great Plains and Pacific Northwest. Thus, in conjunction with peer-reviewed publications, we will develop and deliver research based outreach management recommendations for weed management in crops undergoing moisture and virus stresses with the ultimate goal of reducing the dependence on off-farm inputs while securing yields. <P>This project will generate specific outcomes that will include an assessment of the relative importance of weeds as hosts of WSMV as well as integrated management approaches of weeds and viruses. We will determine the best weed management techniques to maximize crop yield when the crop is at particular risk of becoming infected with WSMV under different weed pressure and water availability scenarios. Finally, as part of our extension responsibilities, we will develop a research-based education and extension program to disseminate our research results and evaluate their impact via surveys of growers and county extension agents. <P>Overall, this information will increase producer awareness of proper crop volunteer and grassy weed management to maximize yield and to prevent losses to diseases including viruses.
Non-Technical Summary: In the Great Plains and Pacific Northwest, the concentration of wheat production has resulted in the influx of specialized pest complexes threatening the economic and environmental sustainability of the small grain production system. Stakeholders across the region have identified wheat viruses and grassy weeds as having major impacts on yield and grain quality. Not only can grassy weeds and volunteer wheat reduce soil moisture and crop yield, they are known as a host for several viruses including Wheat streak mosaic virus, High Plains virus, Triticum mosaic virus, and the arthropod vector of all three viruses, the wheat curl mite (Eriphyes tulipae). The goal of this project is to provide joint weed control and virus management recommendations for small grain growers throughout the Great Plains and PNW. We will achieve this goal by assessing the interrelationships between crop stress including soil moisture, viruses, and weeds on achievable wheat yields. We will investigate solutions to preventing virus epidemics by evaluating the susceptibility of crop varieties and weed biotypes to virus infection by wheat viruses including Wheat streak mosaic virus, High Plains virus, and a newly identified virus, Triticum mosaic virus. Educational efforts will be integral to the success of this proposal in changing crop management practices throughout the Great Plains and Pacific Northwest. Thus, in conjunction with peer-reviewed publications, we will develop and deliver research based outreach management recommendations for weed management in crops undergoing moisture and virus stresses with the ultimate goal of reducing the dependence on off-farm inputs while securing yields. <P> Approach: The first objective, an assessment of the importance of soil moisture and virus stress on crop-grassy weed competitive interactions, will be performed as a field experiment in Bozeman, MT. The experiment will follow a split-split -plot randomized block design with four replications. The site will be planted with virus-susceptible winter wheat variety. Main plots will consist of soil moisture (dryland or flood irrigated); sub-plots will consist of all combinations of presence and absence of grassy weed species and Wheat streak mosaic virus (WSMV), and each sub-sub plot will consist of grassy weed removal at Zadoks 11, 21, 22, 24, and season-long weed control. Seeds of downy brome, green foxtail, and wild oat will be will be used for this study as they are among the most problematic annual grassy weeds occurring in the northern Great Plains. WSMV inoculations will be performed in the spring with a high pressure spray. The impact of moisture, virus, and weeds on stand establishment will be evaluated by measuring plant density, biomass and yield. For the second objective we will evaluate the response of crop variety and weed biotypes to wheat viruses found in the Great Plains region. Seeds of at least three major grassy weed species and the top three wheat varieties in each of six states will be collected from Montana, Idaho, Colorado, Nebraska, Oklahoma, and Texas to determine their relative susceptibility to strains of 3 wheat viruses (WSMV, High Plains virus (HPV), and Triticum mosaic virus (TriMV)). While three of these States infrequently experience wheat virus disease problems the other three have virus epidemics nearly every year. Wheat varieties and weed biotypes will be mechanically- or mite-inoculated with virus and disease progression measured with quantitative ELISA. We will also assess the ability of the wheat curl mite to transmit the three wheat viruses. The third objective is to develop and deliver a research-based educational program on the joint management of grassy weeds and virus under different environmental conditions. We will develop and deliver research based material for on- and off-farm presentations and supporting technical bulletins that translate into simple terms the complicated interactions between management practices and pest dynamics. This material will be presented at many local and regional stakeholder activities. During the three year duration of this project, we expect to directly reach an audience of least 5,000 growers and agricultural professionals. Additionally, we will publish extension bulletins and news releases which will also be posted on relevant web sites. We will present the findings and recommendations of our research on a weekly TV program with an estimated audience of 20,000 households, and in various radio appearances. Each radio appearance reaches an audience of approximately 20,000. Evaluation plans include pre/post tests during our outreach-extension meetings. Implementation will be measured by asking extension agents how many producers are concerned about weeds and plant viruses, and how many producers are adopting our management recommendations.