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April 6, 2006 Spring Snow Melt May Reveal Patchy Lawns
With the surprisingly fast meltdown of the snow recently, many homeowners discovered the snow blanket that had been in place since last Thanksgiving was hiding turf diseases known as snow molds. In North Dakota, the two most common types of snow mold are pink snow mold (also known as Fusarium, or Microdochium, patch) and grey snow mold (Typhula blight). These diseases can affect Kentucky bluegrass and other cool-season grasses. Symptoms for the more common grey snow mold include straw-colored, circular patches. Grey mold growth may appear on the matted grass or along patch perimeters. As long as the grass remains cold and wet, the patches can expand. Hard, fungal bodies, called sclerotia, may be visible on or in leaves and crowns of the affected area. Depending on the species of fungus, these sclerotia may be black or brown and may range from pinhead size to 3/16-inch in diameter. Pink snow mold symptoms differ slightly from those of grey mold. The yellowish to bleached patches may be up to a foot in diameter. Sometimes, a pinkish or off-white cast can be seen on the affected areas, especially under wet conditions. Unlike grey snow mold, no sclerotia are formed. In both cases, the grass leaves may be killed, but the crowns of the grass are seldom damaged. For home lawns, management recommendations for these diseases are similar and focus on cultural practices, rather than the use of chemicals. Contact fungicides are usually useful only when applied before snow cover occurs for an extended period of time. These fungicides typically are not effective if they are applied after symptoms are observed in the spring. Furthermore, fungicides also are not recommended for home lawns since, in almost all cases, modest efforts focusing on cultural practices usually allow the grass to recover. Turfgrass damaged by both pink and gray snow mold usually will recover as temperatures increase and growth resumes. Briskly raking the affected areas with a leaf or broom rake will remove the debris and speed the recovery process. If snow mold is a chronic problem, check your cultural practices. Avoid excessive nitrogen fertilization going into the fall because it prevents the grass from hardening off. Compacted soil also will encourage snow mold growth because it retains moisture long enough to get the pathogen established. Core aeration during the growing season while the grass is growing actively will help mitigate the problem. Finally, make the last mowing about an inch shorter than what was practiced during the season and collect the clippings. This practice, along with raking fallen leaves, removes or greatly reduces the medium for either of these pathogens to thrive. If portions of the lawn have been severely thinned, the affected areas may need to be reseeded. ### Source: Ron
Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu |
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North Dakota State University |
