Winter wheat at risk for disease

Fall disease potential in winter wheat due to the warm, wet weather is expected to be on the rise. Favorable conditions for stripe rust and wheat streak mosaic virus are resurging due to the third year in a row of extended mild weather in the fall without snowfall or significantly hard freezing temperatures. Breaking the green bridge areas has been difficult due to rainfall and a reluctance to apply too many inputs including glyphosate due to the low price of wheat.

For stripe rust, symptoms on winter wheat do not occur in the classic stripes. They are discrete dots. Stripes form in the spring with higher temperatures. All winter wheat varieties are susceptible prior to jointing. If a variety is resistant, the resistance will activate after jointing and higher temperatures.

However, cold temperatures will not kill all the rust – new strains overwinter quite happily in Montana. Growers should prepare for early fungicide application in the coming spring.

Long story short, plant resistant varieties for best management. Those with susceptible varieties for stripe rust should plan on a fungicide application at tilling and, depending on weather, may need another application at flag timing for best results.

For wheat streak mosaic virus, winter wheat planted early and volunteer in high risk areas will be prone to infection and should be monitored closely as temperatures rise this coming spring.

– Jack Stivers is the Lake County Extension Agent for Montana State University.