Brown Patch is a common turf disease that occurs every year in eastern Nebraska, caused by the fungus Rhizoctonia solani. In home lawns, brown patch is found on bluegrass and perennial rye, and it's the most common disease affecting tall fescue, which is usually very disease resistant. The same fungus also infects zoysiagrass, resulting in a disease called large patch.
Brown patch and large patch have similar symptoms, starting with dead grass blades scattered through the lawn, forming circular or semi-circular patterns. Plants do not die completely, so instead of distinct dead patches, homeowners see a generalized browning through sections of the lawn.
The pattern of damaged grass may start with small areas, but can expand up to several feet in diameter. Often the center of patch, which was affected first, will recover resulting in a doughnut-shaped pattern in the grass when homeowners finally notice it.
Lawns that are heavily infected may show uniform browning, without circular patterns.
Close examination of the leaves shows long, irregular leaf spots that are light tan or whitish in color. The margins of leaf spots are dark brown or purplish-black.
Hot, humid weather with daytime temperatures of 85 degrees or above, and nighttime temperatures over 60 degrees are most conducive to the development of Brown Patch. So it usually doesn't start to appear in lawns until mid-summer, and will become less active when cooler temperatures return in fall.
Brown patch kills grass leaf blades, but it does not affect the plant crown. So once the disease is controlled, or becomes inactive, the lawn will recover. A minor infection can be managed with good turf management techniques that minimize infection and promote good grass growth.
Drought Symptoms May Mimic Brown Patch
Damage from brown patch should not be confused with the natural physiological response that occurs when drought-stressed grass is mowed, leaving behind brown streaks that follow the path of the mower. If brown patch is the cause of the problem, the leaf spots described above will be easily found.
Brown Patch Management
Poorly drained soil, excessive thatch and evening irrigation all increase a lawn's susceptibility to brown patch by lengthening periods of leaf wetness, and providing good conditions for fungal spore growth. Brown Patch occurs most commonly on dense, heavily fertilized and watered lawns. Lawns that are heavily fertilized in spring put on lush, succulent growth that is very susceptible to infection.
Using a dull mower blade also increases the possibility of infection. A dull blade shreds the leaf tip, creating larger wounds for fungal spores to enter. A sharp mower blade makes a neat, even cut with a smaller surface area for infection.
A homeowner can reduce brown patch severity with these techniques.
- Water grass in the morning and make no more than two applications of water per week. Apply a half-inch of water at a time. Bluegrass lawns may need a third weekly irrigation in the very hottest parts of July and August.
- Remove and dispose of grass clippings from infected areas of the lawn.
- Frequently sharpen the mower blade.
Fungicide Applications
A severe brown patch infection may warrant the use of fungicides. On lawns with a history of the disease, begin fungicide applications when nighttime low temperatures reach 60° F or warmer, and stop when nighttime lows are below 60° F for five consecutive days. Applications should be made on 14 to 28 day intervals depending on the product used; follow label directions on reapplications.
Look for these active ingredients on turfgrass fungicide products available at your local lawn and garden center.
- Myclobutanil
- Chlorothalonil
- Mancozeb
- Propiconazole
- Thiophanate-methyl
- Triadimefon
Commercial lawn care companies may use one of the products listed above or a product called Heritage (azoxystrobin), which is only available to commercial pesticide applicators.
It will take several weeks before the turf can put on enough growth that the damaged areas are no longer visible, but the grass will recover.
For more information, visit Brown Patch Disease of Turfgrass