Leaf spot disease produces many symptoms. The symptoms you encounter depend on the weather, the particular fungus involved, and the variety of grass you are growing. Excess thatch, heavy nitrogen fertilizing, excess shade, mowing too close, and broadleaf herbicides promote leaf spot.

Leaf spot occurs in warm weather and is easily recognized. Spots on the leaves develop purplish-red to purplish-brown borders and brown to tan centers. The spots may be as wide as the leaf and somewhat longer than wide. Leaf spots may cause the death of leaf tips. However, the fungus can also attack the crown and basal parts of the plants. This occurs especially in the spring, and can cause extensive dieback of the grass. Sometimes plants die in large, irregular patches several inches up to many feet in size. This may produce an irregular patchwork across an entire lawn.

Grass varieties differ greatly in susceptibility; many new varieties are resistant to leaf spot. In addition, you can greatly reduce the severity of attack by following good cultural practices.

• When mowing, cut high, two and one-half to three inches or above.
• Fertilize lawns of susceptible varieties, primarily in the fall. If you apply nitrogen heavily in spring, it will increase the likelihood of leaf spot.
• Watering should be deep, thorough, and no more often than needed. You want grass blades to dry quickly.
• Overseeding disease-thinned lawns with resistant varieties is also helpful in correcting the problem on a long-term basis.

You also can also use fungicides to help protect the lawn and supplement cultural practices.

For current fungicide recommendations, contact your local county Extension Office.

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