Large patch Fungal Disease

Large Patch usually appears as circular or irregular patches of off-color turf. Patches may start a few inches wide but can expand to several feet across. The outer edge of the patch may appear orange, yellow, bronze, or reddish-brown when the disease is active.

In zoysia, centipede, and St. Augustine lawns, the grass inside the patch may look thin, weak, or sunken. During active infection, the leaf sheaths near the base of the plant may become dark, rotted, or easily pulled away.

Large Patch develops when warm-season grass is stressed and weather conditions favor fungal activity. It is most common during cool, wet periods in spring and fall, especially when soil temperatures are mild and the lawn stays wet for long periods.

The disease is often worse in lawns that are overwatered, have poor drainage, excessive thatch, compacted soil, or heavy nitrogen applied too late in the season. Warm-season grasses are most vulnerable when they are slowing down before dormancy or greening up after winter.

Prevent Large Patch by reducing excess moisture and keeping warm-season lawns healthy without forcing too much growth at the wrong time. Water deeply but infrequently, water early in the morning, and avoid evening irrigation.

Avoid heavy nitrogen applications in fall when warm-season grass is preparing for dormancy. Improve drainage, reduce thatch when needed, and mow at the proper height for your grass type. If your lawn has a history of Large Patch, preventive fungicide applications in fall and sometimes spring can help reduce outbreaks.

Use a lawn fungicide labeled for Large Patch and safe for your specific grass type. For lawns with a history of the disease, fall preventive applications are usually the most important because infection often begins before symptoms become obvious.

Apply fungicide according to the label and water it in if directed. For severe or recurring Large Patch, repeat applications may be needed based on the product label. Rotate fungicide groups when making multiple applications to reduce resistance risk.