Brown patches on lawn

What Causes Brown Patches on Lawns?

Your grass was beautiful all summer long, but once the mercury began to fall, brown patches appeared on your lawn. It’s a common story. Environmental conditions such as dense shade, poor drainage, poor airflow and overwatering can invite disease like brown patch, large patch or dollar spot any time of year. But even the best kept lawns in our area are susceptible to fungal attack in the fall and spring, when the temperatures tend to be moderate and moisture levels higher.

Brown patches on lawn Large Patch or Brown Patch

The most common disease affecting grass in our area, a fungus called rhizoctonia manifests as large patch in warm season grasses and brown patch in cool season grasses. Warm season varieties like Bermuda, zoysia and centipede are particularly vulnerable this time of year when vigorous summer growth slows for the transition into dormancy.

As the name suggests, large patch causes sizeable areas of diseased grass in an otherwise healthy lawn. Damage is often circular and can range from less than three feet to 25 feet in diameter. The foliage typically dies back from the leaf tip toward the base, and the more recently affected grass along the edges may appear orange.

In cool season grasses, like tall fescue, brown patch may cause rings or patches of damaged grass measuring five inches to 10 feet or more in diameter. Leaf spots may be noticeable on broader leafed varieties, and new leaves may attempt to grow within a blighted area.

Brown patches on lawn Dollar Spot

Another prevalent disease, dollar spot also causes brown patches on lawns with both warm and cool season grasses. This white, web-like fungus branches out from one blade to the next, infecting the grass in small round spots. The fungus secretes toxins that cause white lesions on the grass blades, multiplying and expanding until the green color disappears from the blade completely.

The telltale round and sunken spots usually range from half an inch to four inches in diameter and appear white, straw yellow or light brown in color. In more severe cases, the spots may overlap to form large irregular patches.

The disease may spread inadvertently when people, animals, lawn equipment, water or wind move infected grass debris from one area to another. Not only unsightly, the damaged grass often becomes thin and susceptible to weed invasions.

don't use nitrogen fertilizer Prevention and Treatment

To prevent fungal diseases that cause brown patches on lawns, follow these basic lawn maintenance tips.

  • Avoid nitrogen fertilizers after July 15 for warm season grasses
  • Mow regularly, but avoid mowing below recommended height for grass variety
  • Remove excess thatch when deeper than one inch
  • Aerate your lawn once per year
  • Water in the early morning before the dew dries and avoid overwatering
  • Consider thinning the tree canopy in problem areas with dense shade

Few fungicide options are available to homeowners, so if you are already seeing brown patches on your lawn and you suspect fungal disease, contact a lawn professional for treatment. Since pet urine, critter digging and other issues can also damage grass, a professional can help with diagnosis as well.

As always, if you have questions about your lawn, our Certified Turfgrass Professionals are happy to help. Contact them at 770.832.8608 or info@NGTurf.com.

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