Fending Off Zoysia Brown Patch Fungus

Q: My Brookhaven lawn is zoysia and was installed in 2013. For many years it looked fine but a couple years ago it got brown patch fungus. Since then I have tried to control it without success. I’m on my third lawn treatment company and two years ago had most of it resodded. Nothing has worked and the problem is as bad as ever. It seems my choices at this point are to either live with it or switch the whole yard to fescue. Do I have any other options?

A: As soon as I saw that you were asking about zoysia, I had a picture in my mind of your lawn. Zoysia diseases develop slowly. I’m not surprised that it looked fine for some years before deteriorating. I have observed that most zoysia problems are the result of several years of misplaced management.

The first problem that zoysia suffers is overfertilization. Zoysia should be fertilized no more than two or three times a year, starting when it’s at least 80% green in the spring and ending well before the first frost. Most homeowners want their lawns green and lush for as long as possible. They start fertilizing before the roots of the plant are capable of absorbing nutrients and they continue fertilization likewise too long in the fall. The result of this zoysia affection is extra fertilizer being applied and not used each year. It results in plants responding to cold weather more slowly than they should and to drought by remaining green longer than they should.

The second major problem I see is mowing height set too high. Zoysia should be mowed at 2-2 1/2 inches. It’s easy to let the height sneak up on you. Four inch high zoysia looks about as good as two inch high zoysia. But four inch high zoysia contributes to a mat of thatch at the base of the plant which is a great place for disease to develop. Shorter mowing heights allow the grass to dry out and thatch doesn’t seem to be a problem.

So what do I advise for you? First, lay off the fungicides. They will lead you down a slippery slope which will cause you to use more fungicide yet get less control. Know when to irrigate and try to keep your grass as dry as possible. This way you will defeat brown patch and other fungal diseases with less work.

Audrey Gilmore

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