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Home SportsNotes This seems to be the familiar phrase right now from every one in the turfgrass industry here in Ohio. Not only does all this precipitation make it difficult to accomplish the day to day management aspects of turfgrass but the rain, combined with a little heat and high humidity, is fuel to the fire for our next problem on the horizon, BROWN PATCH. Rhizoctonia solani, the fungus that causes brown is active and symptoms of the disease are developing in many locations.

All cool season grasses can be affected. The disease occurs over a fairly wide range of temperatures however, the ideal temperature range for this fungus is between mid 70s to mid 90sº F in the day, and above 65ºF at night. High relative humidity (95% and above) is often the key environmental factor to trigger an out break of this disease. It should be noted that there are a number of other patch diseases caused by other species of Rhizoctonia. The other patch diseases often have somewhat different ideal temperatures, some warmer and some cooler, so diagnosis of the specific pathogen is recommended to select the most affective treatment.

Turfgrass that is grown under conditions of over watering, poor drainage / low lying areas, and limited air movement are particular susceptible to this problem. The disease is noticeable by circular patterns that cover a few inches or several feet in diameter, and as the disease grows under favorable conditions the patches will get larger. A "smoke-ring" of grayish/purple tint may be present on the outer edge of the patch when the disease is active (mainly associated with low cut turf, i.e. - bentgrass (bottom photograph)). Individual leaves will show symptoms of wilting, as the leaf blades begin to turn a purple-green color. This can be seen mainly on low cut turf, or young immature turf. On high cut turfgrass the patches are less distinct and rather irregular and lesions can be observed on the leaves (top photograph: brown patch lesions on tall fescue).

To manage the disease make sure the Turfgrass is not over irrigated and improve drainage & air circulation if needed. There are many fungicides that both control and prevent brown patch, these would include but not limited to the following; the strobilurins (most are excellent), the sterol inhibitors - preventative applications, contact fungicides such as chlorothalonil & fludioxonil, polyoxin D zinc salt, and iprodione.

As a compliment to this posting, a brown patch turf podcast is available.
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Posted by Todd Hicks, Joe Rimelspach, & Mike Boehm