What is Brown Patch?
Brown patch is caused by a species of fungus called Rhizoctonia. It effects all cool season lawn grasses but is especially harmful to ryegrass and tall fescue. Kentucky bluegrass and fine fescues can occasionally be effected but damage is usually minimal in these species. Brown patch also affects a variety of warm season grasses including St. Augustinegrass and Zoysiagrass. It is a foliar disease, meaning it harms the blades of grass but not the crown of the plant or the root system.
What are the symptoms of Brown Patch?
Brown patch appears as circular patches in the lawn that are brownish yellow in color and range from 6 inches to several feet in diameter. The affected leaves usually remain upright, and lesions can be seen on the leaves that are tan in color and irregular in shape with a dark brown border. White, cottony, mycelium can be found on dew-covered turf in the early part of the morning. Brown patch is notable for it's distinctive "smoke ring" that is sometimes visible on the outer edge and it's "frog eye" appearance as grass in the middle recovers giving the area a ringed look.
How Does Brown Patch Happen?
Brown patch is most likely to occur during extended periods of heat and humidity when night-time temperatures remain above 68° F. In addition to heat and humidity, the main factors inviting brown patch are excessive nitrogen and irrigation, lack of air movement, poor soil drainage, excessive thatch, and compacted soils. In other words, stressed and poorly maintained lawns.
How is Brown Patch Controlled?
The best way to deal with brown patch is to avoid it by being on a sound lawn care regimen. Do not over-fertilize, use proper watering practices, aerate and dethatch once in a while and try to provide adequate air movement throughout the lawn area.
Control of brown patch can be achieved through a number of chemical fungicides. When considering fungicides, it's best to deal with a lawn care company with licensed pesticide applicators on staff who are professionally trained to diagnose and treat lawn diseases.
There's not much one can do about the weather but be extra careful not to over-water or over-fertilize during periods of high heat and humidity, and increased night-time temperatures. Not an easy task I know, but that's why lawn care is not as simple as a four step program, it can involve timing, patience, trust, luck, and hard work.