Leaf spot in turf

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

There have been many reports of leaf spot disease on home lawns in Michigan in the last couple weeks. In the past, leaf spot and melting out disease were considered the same disease but recently they have been classified as two different diseases. Despite the different classification, these diseases closely resemble each other, but tend to be active at different times of the year. Leaf spot is generally active during warm summers while melting out is active during cool, wet weather typical of spring.

The symptoms of both diseases are very similar. The initial symptoms are water-soaked spots on leaf blades that turn purple/brown/black. Turf infested with leaf spot or melting out will appear yellowish to reddish-brown and a general thinning of the turf with no distinct pattern may occur if conditions are ideal. The best management strategy to alleviate damage from these diseases is to irrigate lightly and frequently, preferably around mid-day (noon), and apply a light fertilizer application. Avoid irrigating at night because it results in the leaf blades remaining moist throughout the night and therefore more susceptible to disease infection. Another cultural management option is to raise the mowing height to reduce turfgrass stress. Fungicide applications to home lawns are generally not recommended as they can be expensive and often give unpredictable results.

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