MSU students battling wheat mite

A microscopic mite and the disease it carries — wheat streak mosaic — are destroying wheat fields throughout the western Great Plains.

Now Montana State University faculty and students are fighting back through a new collaboration that involves the Agricultural Research Service and six universities in Montana, Colorado, Nebraska, Kansas, Oklahoma and Texas.

The National Institute of Food and Agriculture recently awarded a five-year, $3.4 million grant to be shared by the seven institutions, starting in January 2013. MSU’s portion is $800,000, but an additional $200,000 grant raises that to $1 million. 

Members of MSU’s team said they will use their funds to build on research that has been conducted over 80 years and, here at MSU, over the past six years. One major goal is developing an accurate forecasting model to give farmers additional tools to fight wheat streak mosaic. States in the western Great Plains grow more than 1 billion bushels of wheat a year, approximately half of the wheat produced in the United States. But wheat streak mosaic destroys about 20 million bushels a year.

The MSU team will conduct research, develop educational materials and hold outreach events. They will share their findings and materials with growers, scientists, tribal college students, K-12 students and the general public throughout the six-state region.

Among other things, the MSU researchers said they will test pesticides this winter to see if they can find anything new that might be economical and effective against the vector of the virus, the wheat curl mite. They also want to help figure out why the severity of wheat streak mosaic varies by state. Texas routinely has epidemics of the disease, and wheat grows there continuously, which likely contributes to the problem. Weather, particularly hail events, also plays a role in perpetuating the disease. 

Wheat streak mosaic is the most common wheat virus and the most serious wheat viral disease in the Great Plains, according to the MSU team led by associate professor and Extension plant pathologist Mary Burrows. It might also be the hardest to manage because there are no varieties of wheat that can completely resist it and no pesticides that work against it. Wheat curl mite, the mite that transmits the disease, is so small that it can only be seen under a microscope. Farmers might suspect they have a problem only when they see fields of curling, yellow streaked leaves.

Unfortunately, growers who think they are planting resistant varieties or applying effective pesticides are mistaken, Burrows said. Not only are they wasting their money, but they might make matters worse if they apply the insecticide “imidacloprid.” This chemical compound kills insects it directly contacts, but often increases mite populations by destroying natural enemies. The result is greater spread of wheat streak mosaic.

Zach Miller, an MSU postdoctoral researcher in plant sciences and plant pathology, said the forecasting model that the group plans to develop will encourage more farmers to use Integrated Pest Management. The model will incorporate factors that farmers can manage, such as planting dates, when and how to fertilize, and decisions about wheat varieties and weed management. It will also incorporate factors that are out of farmers’ control, such as weather and biology.

Weed management is important because mites and viruses don’t just hide in wheat, but in weeds and native grasses, said Extension Croplands Weeds Specialist Fabian Menalled, associate professor in MSU’s Department of Land Resources and Environmental Sciences. Menalled has been working to understand how environmental and biological factors affect wheat streak mosaic. At the same time, he has studied the relationship between non-crop plants and the virus.

Burrows, Menalled and Miller are all members of MSU’s wheat streak mosaic team. A fourth member is Irene Grimberg, research associate professor in MSU’s Science Math Resource Center.  Grimberg’s job will be to develop educational materials that Extension agents and others can distribute throughout the six-state region.  Classroom materials will include learning modules based on wheat streak mosaic. They will be aimed at K-12 students in the STEM areas of science, technology, engineering and math. 

The four team members will be assisted by MSU postdoctoral students, graduate students and undergraduates.