Brown Patch and Large Patch of Turfgrass
Under warm and humid conditions, the fungus, Rhizoctonia solani causes brown patch on cool-season turfgrasses such as Fescue and Ryegrass and large patch on warm-season grasses, including Bermuda, Centipede, St. Augustine, and Zoysia grass.
As the name implies, brown patch is characterized by brown or tan patches of diseased turf ranging from 2 to 3 inches in diameter. Symptom development varies according to mowing height. Turfgrass maintained above 1-inch show irregular silver-gray or tan lesions with a thin, dark-brown border. Turfgrass that is maintained below 1-inch, show no distinct lesions but will exhibit dieback. All turfgrass within an affected area may not be mortally damaged within a developing patch; therefore, affected turf may recover once disease pressure is reduced. Areas with poor air movement, soil drainage, and excessive shade are more conducive to disease development. Fertility amendments such as nitrogen can also increase disease pressure since a lush, dense turf is highly susceptible to infection.
Large patch occurs during the spring and fall when warm-season turfgrasses are entering or exiting winter dormancy. Large circular patches ranging in diameter from less than 3.3 feet to 26.4 feet characterize the disease. Disease symptoms are visible on the leaf sheaths, where water-soaked, reddish-brown or black lesions are observed resulting in foliar dieback. Factors such as excessive soil moisture, thatch and lower turf canopy encourage disease development. Environmental factors including poor drainage, shade, restricted air movement, or excessive irrigation increase disease severity.
Minimizing environmental factors through cultural methods and applying a good spray program is the best way to manage this disease in your lawn. Few effective fungicides are available for the general public to use for large patch management, so emphasis should be placed in cultural control methods. For more information about horticulture contact Colby Griffin at 919-496-3344 or firstname.lastname@example.org.