Management practices may reduce infections of wheat streak mosaic virus
Caused by wheat streak mosaic virus (WSMV), wheat streak mosaic disease heavily impacts wheat in the Great Plains, where native grasses provide favorable habitat for the wheat curl mite (WCM).
Wheat curl mites
“WSMV is transmitted through the vector of the WCM. WCMs are microscopic, less than 0.3 millimeters long and can only be seen under magnification,” explains South Dakota State University Extension Plant Pathologist Emanuel Byamukama.
Mites grow from eggs to adults within eight to 10 days, and population densities can grow dramatically over a short period of time.
“WCMs are not capable of moving from plant to plant or from field to field on their own. They are blown by wind to nearby plants. They are however, capable of crawling over short distances between stems or leaves that are in contact with each other,” he continues.
Because wind carries the mites between plants, heavy WSMV infections are often seen along the edges of fields.
“Winter wheat is more impacted by this virus than spring wheat because of the longer infection period for infections that take place in the fall. This disease can also take place in other crops like barley, corn, rye, oats and several other perennial and annual wild grasses,” Byamukama describes.
Symptoms of the disease often appear as pale green and yellow stripes, creating a mosaic pattern of colors. Depending on the variety of wheat that has been infected, the virus can also stunt growth in the plants.
“Symptoms worsen with stress caused by dry and hot weather conditions,” he adds.
A number of cultural practices can be implemented to help control WSMV, including the use of crop rotation.
“We should rotate away from crops that could also host this virus, such as corn, oats or sorghum. We need to use broad leaf crops such as field peas, lentils or sunflowers to help keep pressure low,” remarks Byamukama.
Using resistant wheat varieties or cultivars tolerant to the virus is another management option, as is using delayed planting.
“Planting early in the fall, especially if temperatures are mild, increases the risk of mites landing and transmitting viruses in emerging winter wheat,” he says.
To manage for WSMV, producers can also destroy volunteer wheat or grassy weeds at least two weeks before planting to reduce chances of infection. Volunteer wheat and grassy weeds serve as a “green bridge” when left in the field, allowing for the mites to survive and transfer to the new crop.
“Volunteer wheat and grassy weeds are the most important risk factor for the WCMs and WSMV. Volunteer wheat or weeds can be destroyed through the use of tillage or herbicides,” Byamukama suggests.
Losses from WSMV can vary from negligible to total loss. In some cases, the wheat becomes so stunted that it cannot be picked by the combine.
“This disease can be devastating to wheat. To manage this disease, we need to destroy the green bridge at least two weeks before planting, practice crop rotation and plant resistant or tolerant cultivars,” states Byamukama.
Natasha Wheeler is editor of the Wyoming Livestock Roundup and can be contacted by firstname.lastname@example.org.