The 2021 winter had extended periods of snow cover across the Commonwealth. With the recent (and in some areas rapid) reduction in snow cover, we have received questions about the appearance of snow molds.
It has been several years since we had to deal with this issue, and while snow molds normally do not cause an economic impact on small grains production, it is still important to take into account the symptomology differentiating the different types of snow molds that could impact the crop.
This is especially important if your small grains stand is variable , and you are considering incorporating the small grain and switching to a different row crop in 2021.
Several fungi are responsible for snow molds, including, Microdochium nivale, Globiosporangium spp., and Typhula spp. In all cases, the occurrence of snow molds was favored by an early snowfall, which was then followed by a deep snow on unfrozen ground. When this occurs, the microenvironment is very favorable for fungal growth on the plants throughout the winter months.
Scouting for snow molds often focuses on targeting areas of the field where snow cover was greatest (1′ +). Symptoms will vary depending on the fungus which causes the disease but can range from a pink, fuzzy growth on dead or dying leaves, along with evidence of pinkish-orange fungal structures with pink snow mold, to a gray, brittle tissue symptom that breaks down or crumbles when touched for speckled snow mold.
Another type of symptom which may be observed with snow rot is dark green blotches on leaves of plants, especially in areas of the field that are low and had cold water accumulation.
Currently, there are no chemical control options available for snow molds. Rotating to a legume can reduce the amount of fungus for future crops but it should be mentioned that these fungi can survive for long periods of time in the soil. Check the small grain cultivar to determine if it has resistance to snow molds.
Fall planting date is an important factor to consider as earlier planted fields will survive better when snow mold is favorable given that larger plants are more resistant to infection and can resume growth in the spring better than younger plants.