Dollar Spot Disease on Minnesota Lawns

The appearance of Dollar Spot Disease on Minnesota lawns has appeared a little later than usual this year. Dollar Spot, caused by the fungus Sclerotine Homeocarpa, is most usually brought on by heat and/or drought stress. The symptoms of this disease vary with turfgrass species and with mowing practices. Fortunately, the damage caused by Dollar Spot is not normally severe, and most lawns will, given time, recover on their own. See photos from Cornell University.

Under close mowing, as on a putting green, the disease appears as small, circular, straw-colored spots about the size of a silver dollar. (This is how it got its name.) In higher cut lawn grasses, the patches can be much larger and will often combine to form irregular areas of straw-colored grass.

Early in the morning when dew is still on the lawn, a white cobwebby growth or mycelium of the dollar spot pathogen can sometimes be seen. A key symptom of the disease, however, is an hour-glass shaped, tan-colored lesion that can be seen on individual plant leaves.

Dollar spot disease develops most quickly during periods of warm days, cool nights, and high humidity. It's a very common disease that can afflict nearly all turfgrasses. In helping to control it, it's important to maintain the turf at adequate fertility levels and to try to maintain good air circulation by keeping turf mowed at a proper height and by pruning trees and shrubs that border turf areas whenever feasivle. Properly timed fungicide applications can also help control this disease but the best prevention is to avoid letting the turf go into drought stress.

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