The winter of 2022-23 is shaping up to be a bad snow mold year, especially for those across the Waterville Plateau in Douglas County where snow continues to be present as of March 28. Snow mold is nothing new to this region, as producers have dealt with it dating back to the 1940s.
Wheat varieties can expect to see some level of damage, depending on their level of resistance to the disease, especially if snow has been on the ground for 100 consecutive days or longer. Waterville and the surrounding areas have had continuous snow cover since at least November 15, which is 133 days and counting.
The WSU Douglas County Extension office has fielded numerous calls asking how well the new wheat variety Piranha is going to fair with the disease. Limited ratings in 2021 have it comparable to Mela in the Waterville area and better than Mela out near Mansfield, WA. Time will ultimately tell exactly what disease rating it is going to have (i.e., 1,2 = Resistant; 3,4 = Moderately Resistant; 5 = Moderate; 6,7 = Moderately Susceptible; 8,9 = Susceptible). For additional snow mold ratings, visit the WSU Wheat and Small Grains Variety Selection Tool.
The following information about different varieties of snow mold was written by Dr. Tim Murray, Rosalie and Harold Rea Brown Distinguished Endowed Chair in the Dept. of Plant Pathology at WSU.
Snow mold is a generic name for any one of several diseases that can develop on wheat under snow. The pathogens that cause these diseases are specialized and able to grow in the wet, near-freezing environment under the snow and destroy most of the aboveground foliage. In eastern Washington, snow mold can be caused by one of four different fungal or fungal-like pathogens; however, speckled snow mold and pink snow mold are the most common and destructive. Speckled snow mold is the most destructive disease in eastern Washington and needs about 100 days of continuous snow cover with unfrozen soil before damage is likely to occur. This disease is most common in the wheat-growing area north of Highway 2 beginning about Almira west to Waterville. Pink snow mold can occur alongside speckled snow mold but is favored by slightly wetter conditions and usually doesn’t cause damage to wheat over large areas. Pink snow mold is more widespread than speckled snow mold because it doesn’t require as much snow cover to develop, so it’s also common in golf course turf and home lawns. There is another snow mold fungus that resembles the speckled snow mold fungus that occurs widely in eastern Washington; it is often called gray snow mold or Typhula root and crown rot because it often develops below ground and is distinguished by the reddish-colored speckles that develop on infected plants. This disease causes little damage to wheat but can be very destructive to winter barley.
Most growers in the traditional snow mold area know that planting a resistant variety early is the best way to control snow mold. Outside of the Waterville Plateau, pink and gray snow mold likely will be apparent in some spots when the snow melts. To determine whether snow mold was the cause, look closely at the dead plant parts for evidence of a cob-web-like growth on the surface. With pink snow mold, plants will have a salmon-pink color soon after snow melt; the color will fade leaving brown-colored tissue. For the speckled snow molds, evidence of disease is the presence of dark-colored survival structures known as sclerotia. Plant parts killed by cold may appear light brown or bleached without any of the signs of snow mold. Samples can also be submitted to Plant Disease Clinic for confirmation.
For more information, consult Extension bulletin Snow Mold Disease of Winter Wheat in Washington (EB1880).
For questions or comments, contact Dale Whaley via email at dwhaley@wsu.edu or phone at 509-745-8531.