While Brown Patch can cause fairly large, unsightly brown patches, most lawns eventually recover from this disease.
In home lawns, Brown Patch is usually found on bluegrass, tall fescue, and perennial ryegrass. Symptoms of Brown Patch start with scattered dead grass blades forming a circle or semi-circular pattern in lawns. The circles of affected grass may be up to two feet in diameter, although many are much smaller.
To confirm Brown Patch is the problem, closely examine green grass blades in the affected area. It’s best to do this just prior to mowing, rather than just after mowing. Look for irregular shaped leaf spots that are light tan with reddish margins. Grass in the center of circles may not show any symptoms so inspect the grass on the outside of circular patches for leaf spots.
If leaf spots are found to confirm the disease is active, Brown Patch can be controlled with an application of a fungicide like benomyl or chlorothalonil. These chemicals will not cure current infections. They will protect new grass blades as they emerge from becoming infected. It will take a number of weeks before the lawn puts on enough new growth so damaged areas are no longer visible.
To help reduce the severity of this disease in the future, homeowners should start an overseeding program with cultivars resistant to Brown Patch and other diseases; and use practices that reduce conditions favorable to diseases.
Brown Patch occurs most commonly on dense, heavily fertilized and watered lawns. Lawns that are heavily fertilized in early spring tend to put on lush, succulent growth that is very susceptible to disease. By using a late fall fertilization, you can avoid the need to fertilize too early in spring.
Fungal spores require moisture to grow and infect leaf blades. Poorly drained soil, excessive thatch and evening irrigation all increase a lawn's susceptibility to disease. Core aerate (plug) lawns to improve drainage. If an excessive thatch layer exists power rake in April or September to reduce it.
Irrigate lawns in the early morning hours so the grass will dry quicker. When watering, moisten the soil four to six inches deep; then wait to water until the grass shows signs of needing irrigation. Light, daily irrigations can promote disease.
Using a dull mower blade will also increase a lawns susceptibility to disease. Dull blades shred the ends of grass blades, creating a larger wound for fungal spores to enter. A sharp mower blade makes a quick, even cut with a smaller surface area for infection.
When a foliar disease like Brown Patch is present, remove and dispose of grass clippings from infected areas of the lawn. Once the disease is under control, clippings can be left on the lawn again. Leaving clippings is beneficial to a lawn and will not contribute to thatch.
Source: Kelly Feehan, Extension Educator
Ann Fenton
University of Nebraska Extension
Pierce County
