Snow Mold of Cereals
Something went wrong. Please try again later...
Pathogen Facts
- The term “snow mold” is a blanket term for any of the several fungal diseases that develop on cereal crops underneath snow.
- The most common snow molds are pink snow mold, Typhula rot (called gray or speckled snow mold), and Sclerotinia snow mold.
- This disease only occurs in areas that receive dense layers of snow prior to soil freezing.
Snow mold symptoms in a field trial. Photo courtesy of Sam Tragesser, Senior Research Associate.
Conditions Favoring Disease
- These fungi perform best at 68 °F (20 °C) but they can infect plants at temperatures as low as 32 °F (0 °C).
- Snow on top of unfrozen soil provides cold, dark, and humid conditions that are favorable for these microorganisms.
- Areas of the field with thicker layers of snow cover are more conducive for infection and will typically show more severe symptoms.
- Early-planted wheat is more likely to become infected due to lush growth which can aid in the transmission of the fungi from plant to plant.
- Once temperatures warm and fields dry out in the spring, disease development will halt.
Identification
Pink Snow Mold
- Caused by the fungal pathogen Microdochium nivale (Fusarium nivale).
- Pink coloration develops on the leaf surfaces from masses of conidia (asexual spores)
- Mild winters with more moisture are more favorable for this snow mold.
Gray/Speckled Snow Mold
- Caused by the fungus Typhula incarnata and Typhula ishikariensis
- White to gray mycelial mat with dark colored sclerotia give the characteristic “speckled” appearance on infected tissue.
- Speckles can range from darker colors to reddish spots
- Needs 100 days of continuous snow cover paired with unfrozen ground.
Sclerotinia Snow Mold
- Caused by the pathogen Sclerotinia borealis.
- Very similar in appearance to speckled snow mold but overwintering structures are larger and darker sclerotia
Management Considerations
- Selecting resistant cultivars and varieties can lessen the severity of infection.
- No variety is completely resistant.
- Crop rotations away from winter cereals can reduce the build up of inoculum in the growing system
- No-till seeding has proven to be effective at mitigating the severity of disease
References
Frank, E., Evans, K., Barnhill, J., & Pace, M. 2008. Snow Mold on Small Grains. Retrieved from Utah Pests Fact Sheet: https://utahpests.usu.edu/uppdl/files ou/factsheet/snow-mold-grain08.pdf McBeath, J. H. 2002. Snow Mold-Plant-Antagonist Interactions: Survival of the Fittest under the Snow. Retrieved from American Phytopathological Society: https://www.apsnet.org/edcenter/apsnetfeatures/Pages/SnowMold.aspx