Potential Winter Wheat Diseases

Jesse Fulbright, MSU Liberty County Extension

With much of the snow having melted or melting out of the fields I wanted to turn people’s attention to the thought of potential diseases in our winter wheat due to the excessive snow cover.  Much of this information comes from Mary Burrows, Extension plant pathologist and a Montana Ag Alert that she put out to statewide producers last week.

First, let’s talk about snow mold.  Snow mold occurs on fall-planted crops under prolonged snow cover or wet conditions with freezing temperatures.  If you see patches of fields with dead plants, look towards the edge of the patches at the sick plants.  If you see lesions on leaves with a tan center and brown halo, this is likely pink snow mold, which is the most common snow mold we see here in Montana.  The good news is that this disease will not infect the spring crop, it requires extended low temperatures and moisture.  It is favored by cool wet falls and continuous winter wheat planting.  There may be a difference in varieties. There is another snow mold commonly referred to as ‘speckled’ snow mold.  Dead plants won’t recover, but if the plants are tillering and have a good root system they should pull out of it.  There is no risk of the fungus spreading to a spring crop should you seed spring wheat nearby.  If replanting, please use good management practices to prevent Rhizoctonia root rot if soil conditions continue to be cool and wet.

Snow mold patches on winter wheat caused by Microdochium nivale and
Myriosclerotinia borealis (Photo courtesy of apsnet.org)

 Rhizoctonia root rot (bare patch) can be partially controlled by seed treatment and by crop rotation, good weed control, and eliminating the ‘green bridge.’  This is a ubiquitous fungus in the soil with a broad host range that prefers cool, wet springs.  Usually you won’t see complete devastation in a field, but if you’ve ever had very shallow-rooted plants and uneven height in the field, likely Rhizoctonia was involved.  Use a good seed treatment with efficacy against Rhizoctonia if you suspect you may have had a problem in the past.