Gray leaf spot Fungal Disease

Gray Leaf Spot usually starts as small brown, tan, or gray spots on individual grass blades. As the disease progresses, the spots may become oval or elongated with darker brown or purple borders.

In severe cases, the tips of the grass blades may turn brown, twist, or die back. In St. Augustine grass, Gray Leaf Spot can create thin, scorched-looking areas across the lawn. In ryegrass or young tall fescue, it can spread quickly and cause major thinning during hot, humid weather.

Gray Leaf Spot develops when heat, humidity, and extended leaf wetness create ideal conditions for fungal activity. It spreads more aggressively when grass stays wet overnight, when airflow is poor, or when lawns are under summer stress.

The disease can be made worse by heavy nitrogen applications during hot, humid weather, frequent light watering, mowing wet grass, dull mower blades, and heavy traffic on stressed turf. Young seedlings and newly established lawns can be especially vulnerable.

Prevent Gray Leaf Spot by reducing leaf wetness and avoiding excess nitrogen during disease-prone weather. Water early in the morning, avoid evening irrigation, mow with a sharp blade, and avoid mowing when the grass is wet.

Improve airflow where possible, reduce excess thatch, and avoid pushing soft, fast growth with heavy quick-release nitrogen in the heat of summer. For lawns with a history of Gray Leaf Spot, preventive fungicide applications may be needed when hot, humid conditions begin.

Use a lawn fungicide labeled for Gray Leaf Spot and safe for your specific grass type. Apply at the first sign of disease or preventively when conditions are favorable, especially on susceptible lawns such as St. Augustine, perennial ryegrass, or young tall fescue.

For repeat applications, rotate fungicide groups to help reduce resistance risk. Pair fungicide treatment with better watering, mowing, and fertility practices so the lawn has the best chance to recover.