Brown Patches on Lawns

Dry brown patches on lawns can be caused from winter drying, dog urine, or snow mold. The only way one can be sure that the brown spots are snow mold is to look for the major causal organisms, the fungi Typhula incarnata, and Sclerotinis borealis, under the microscope. Early in the spring snow mold begins to grow under the snow, and can be seen growing on their lawn as a white filamentous material. If you have seen this you should rake the dead spots on your lawn and apply a registered fungicide as a root drench, to the soil. This area of the lawn will need to be reseeded. Later on you may also want to fertilize your lawn, after grass emergence.

To prevent snow mold from harming your lawn you could also spray the lawn with a registered fungicide in the early fall. The growth of snow mold is a function of the winter weather, therefore this preventative measure does not always work. Recent research at the University of Guelph has reported that top dressing lawns and golf course greens in the fall with finely divided municipal compost also inhibits the snow molds in Ontario.

Compiled by: Dr. Bill Paton and Vicki East