How to Treat Brown Patch Fungus in Your Lawn
Common Causes and the Best Fixes for Landscaping
Fungal infections, insects, pet urine, and heavy foot traffic can cause brown, dead grass patches on your lawn. Specifically, brown patch disease is a fungal infection usually caused by Rhizoctonia solani. The fungus often appears mid to late summer when the weather is hot and humid. Brown patch is a foliar disease, meaning that it harms the blades of grass but not the plant's crown or root system.
Rhizoctonia can affect all cool-season lawn grasses but is especially harmful to ryegrass and tall fescue. Kentucky bluegrass and fine fescues can occasionally be affected, but the damage is usually minimal in these species. Brown patch can also affect a variety of warm-season grasses, including St. Augustine grass and zoysiagrass.
Causes of Brown Patches in Lawns
- Brown patch fungus: The main factors causing this fungus are excessive nitrogen and irrigation, lack of air movement, poor soil drainage, excessive thatch, and compacted soils. It can strike lush, green lawns and poorly maintained lawns. Sometimes, improving environmental problems, such as increasing air circulation, may be enough to eradicate a fungal issue. For persistent problems, you might need to move on to a fungicide and reseed with fungal-resistant varieties of grasses.
- Grubs: Grubs eat grass roots, leading to small brown patches that widen into larger spots. Walking over grass patches affected by grubs feels sponge-like and is easily raked up because the roots are damaged. Treat the grubs with insecticide in the spring and reseed the grass in the fall.
- Excessive thatch: Grass that is not properly watered, fed, or mowed can accumulate dead and decaying plant material between the plant leaf blades and the root system. Sometimes, grass tries to grow roots in the thatch, but since it can't hold water, the plants dry out and cause brown spots. Dethatch and aerate the lawn to fix this problem.
- Pet urine: Dog urine burns are caused by the high amount of nitrogen in the urine. It appears like brown centers and dark green outer rings. Water deeply to wash away the salts in the urine, aerate the spot to encourage new grass to grow, reseed the spot, or use a dog urine lawn treatment product.
- Foot traffic and leaving objects on the grass: A lot of foot traffic, like playing football or soccer, or leaving a baby pool out for more than a few hours, can be enough to kill grass and leave brown patches over the lawn. Remove objects each day from the lawn. Also, consider playing on the lawn in different spots or lessening the frequency so grass can recover from foot traffic damage.
Common Seasons for Brown Patch Fungus
Grass fungus usually does not go away on its own. It’s also easy to spread fungus via foot traffic and grass clippings, so immediate treatment is important. Begin brown patch control in the spring with aeration and dethatching. Apply fungicide when the fungal patches appear (usually in mid to late summer). Reseed with different grass species by over-seeding over several fall seasons. For quicker results, eliminate the old turf grasses in spring and reseed them immediately.
The Rhizoctonia fungus may be present for some time in the soil before it manifests as brown patch disease. The fungus overwinters in the lawn grass or soil beneath in the form of fungal bodies known as sclerotia, and it can survive for years until conditions are right.
Rhizoctonia is most likely to cause brown patches during periods of high temperature and high humidity in mid to late summer when night-time temperatures remain above 68 degrees Fahrenheit and daytime temperatures are routinely in the 80s or above. Periods of rainy weather when the air is saturated with moisture may also prompt the disease to emerge.
Warning
Fungicide powders and sprays are typically less toxic to pets and humans than herbicides and pesticides. Still, some are known to irritate the eyes or throat. More severe health problems are possible for individuals who repeatedly use fungicides or have high exposure.
What You'll Need
Equipment / Tools
- Bow rake or dethatcher
- Lawn aerator (can be rented)
- Pressure sprayer
Materials
- Lawn fungicide (if needed)
- Fungus-resistant grass seed (if needed)
Instructions
How to Treat Brown Patch Fungus on Lawns
Eradicating brown patch disease may not require all of the following steps. You can stop work when the efforts show results. The time and effort required will depend entirely on the severity and persistence of the fungus—minor problems may be very easy to solve, while combatting widespread infestation can be a year-long endeavor. Always try to control brown patch fungus by adjusting cultural practices before reaching for chemical fungicides.
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Diagnose the Disease
Brown patch appears as irregular circular patches in the lawn that are brownish-yellow and range from 6 inches to several feet in diameter. The affected leaves usually remain upright, and close inspection shows lesions on the leaves that are tan and irregular in shape with a dark brown border. White, cottony mycelium can be found on dew-covered turf early in the morning.
The ring itself is most visible in the morning. Sometimes grass within the circle is entirely killed, creating a sunken look to the patch, but more often, the grass inside the patch simply becomes thinner than the surrounding lawn.
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Improve Air Circulation
Many cases of brown patch can be cured simply by improving air circulation in the lawn, which reduces the humidity that favors the fungus. The best way to do this is to aerate and dethatch the lawn annually.
Dethatching can be done manually, with a stiff bow rake or dethatching rake, or with power equipment available for lease at home centers and tool rental outlets. Aeration is usually done with a power rental tool or a hired professional lawn service.
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Change Cultural Practices
Brown patch fungus thrives in wet, fertile conditions, so the response to ongoing lawn problems is to reduce feeding of your lawn and make sure watering practices are appropriate.
Avoid feeding your lawn during hot and humid weather, and reduce the fertilizer used. Fertilizer manufacturers often recommend repeated heavy feedings, but your lawn is often healthier with just one or two light feedings each year.
Watering is probably unnecessary if you are getting 1 inch of rainfall per week, But if you do water, do it early in the day so the grass can dry out thoroughly before nightfall. If dew is collecting on your lawn each morning, your lawn probably does not need to be irrigated. You can remove condensation by dragging a water hose over the lawn, lowering the humidity that causes brown patch disease.
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Apply Fungicide
Lawn care experts say fungicide treatment is appropriate for high-value ryegrass and bentgrass turf blends; most lawns typically recover without chemical treatments.
The first fungicide spray should be applied immediately after the symptoms, especially if hot and humid weather is expected. Although homeowners can purchase fungicides, it's best to deal with a lawn care company staffed by professionals trained to diagnose and treat lawn diseases.
As with any chemical application, it's best to spot-treat diseased areas rather than apply chemicals broadly over the entire lawn.
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Reseed With Resistant Grass Varieties
Where all other efforts fail, you may need to reseed with a turfgrass variety that has known resistance to this fungus. A variety of grasses are available with moderate resistance to the Rhizoctonia fungus. If a brown patch is an annual occurrence, consider top-seeding your lawn with resistant grasses. Check with your local university extension service for recommendations for resistant grass species.
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How do I treat brown patches on my lawn?
Although there can be several reasons for brown patches on lawns, they all have one thing in common, dead grass on top. Remove the dead layer, treat the cause of the brown patch, and reseed if necessary.
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Will grass recover from brown patch?
Grass can recover from brown patches, but it can take some time. Depending on when it occurs, you might need to wait until the next growing season until reseeding takes hold.
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How do I get rid of brown patch fungus on my lawn naturally?
Spray a solution of water mixed with a couple of pinches of baking soda and a few drops of vegetable oil on the spot. Reapply this spray every three days. Do not add a lot of baking soda since it can raise the alkalinity of the soil. Another solution is to spray neem oil on the spot, repeating as necessary until it disappears.