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No Fun in Fungus

Your gorgeous green lawn can quickly be decimated by brown patch or large patch (its common names), a fungal disease caused by different strains of Rhizoctonia solani. The disease can develop rapidly when air temperatures and humidity add up to 150 degrees, nighttime temperatures are above 60 degrees, or there is a prolonged period of leaf wetness. All grasses are susceptible, but at different times of year. Generally, cool-season grasses (fall fescue, ryegrass, bluegrass, and bentgrass) start displaying symptoms during late spring, and it can also occur in these grasses during warmer periods of winter months. Warm-season grasses (St. Augustine Grass, Zoysia Grass, Bermuda Grass, and Centipede Grass) are most commonly affected during early spring or late fall. How can you tell if you have a fungus in your lawn?

Brown Patch - Fungus - Tennessee


Symptoms can vary depending on the type of grass and soil conditions. Brown patch and large patch generally cause thin patches of light brown grass that are roughly circular and can be as small as a dinner plate to as large as a car hood. If not contained, more and more spots will form, and they will eventually connect. 

You can also examine the grass blades for evidence of this disease. Looking closely at cool-season grasses, the grass blades will have small, irregular, tan leaf spots with dark brown borders. Infected warm-season grasses rarely have leaf spots but instead have rotted leaf sheaths near the soil.

How to prevent brown patch

The best way to prevent brown patch or large patch is to follow good lawn care practices. We’ve come up with a few tips that will help prevent this fungus from taking over:

-Water grass only when needed and to a depth of four to six inches monthly (about 1 inch of water per week). Our experts recommend watering early in the morning, so the grass has time to dry during the day. Remember, if water sits on your grass for an extended period, it’s considered an ideal fungi growing condition.

-Avoid fertilizer with high rates of nitrogen in late spring and summer for cool-season grasses and in mid to late fall or early spring for warm-season grasses. The disease-causing fungi readliy attacks lush growth that nitrogen promotes.

-Keep lawns mowed at an optimum height for your grass species (Bermuda and Zoysia – 2 to 2 1/2 inches, fescue – 3 1/2 inches). Also, keep those blades sharp! You’ll minimize disease entry points with a nice clean cut. Plus, your grass will look nicer instead of looking shredded.

-Provide good drainage. Don’t let moisture pool and attract fungi.

How to treat brown patch

If you’ve already got it, we’re sorry. Take heart, Williamson County! There is a way you can get your lawn back. Fungicide! There are many options when it comes to choosing a fungicide. Whatever you choose, you’ll most likely be doing at least a few treatments until you see signs of improvement. Most good fungicides will last 28-30 days, and a less expensive fungicide will only last 10-14 days. Keep in mind that it will help in disease control to alternate fungicides. You don’t have to alternate every treatment, but every season is helpful to prevent a buildup of resistance. If you’ve never applied fungicide before, get a liquid. You’ll have better control.

Our experts at Pure Green enjoy talking about fungus, mowing, watering and general lawn maintenance. It’s what we do best and we love taking care of lawns in Franklin and Brentwood! If you’ve got questions about your lawn, call us for a free estimate.