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The Top 5 Common Lawn Diseases and How to Treat Them

Posted on May 26th, 2023

Lawn diseases can be a hidden menace that causes a significant impact on the health and appearance of your carefully cultivated lawn. Knowing how to recognize and address common lawn diseases is essential in maintaining a thriving turf. It also helps reduce additional complications and related maintenance expenses.

In this blog, we list common lawn diseases, their symptoms and prevention and treatment tips.

1. Brown Patch

Brown patch is a fungal disease caused by Rhizoctonia solani, which flourishes in turf that receives excessive water and fertilizer. These circular patches are brownish-yellow with a diameter ranging from six inches to several feet. They usually appear in early spring or late summer, as fungal outbreaks are more prevalent during extended heat or humidity periods.

Brown patch affects various types of grasses, including:

  • Cool-season lawn grasses with ryegrass and tall fescue being particularly vulnerable
  • Kentucky bluegrass
  • Fine fescues
  • Warm-season grasses such as St. Augustine grass and Zoysia grass

If the disease has been active for a while, the inside of the patch may show signs of recovery. It will often leave a ring of dead grass around it.

Grubs, which feed on grass roots, can damage your lawn and lead to brown sponge-like patches that eventually widen. They can roll up when raked due to the root damage.


Applying fungicides can help treat active diseases and prevent future problems from listed fungi.

First, remove the dead grass by raking the affected area to repair grub patches. Then apply an appropriate amount of grub control product. Similarly, using a suitable fungicide can help manage the disease and promote healthy recovery of the affected areas.

If the brown patches persist or worsen despite treatment, it’s best to consult a professional lawn care service for better results.

2. Leaf Spot

Leaf spot is another common lawn disease that first appears as small dark purple to black spots. As the spots grow in size, their centers often turn light tan. In cooler months, the disease is confined to the leaf blades but may spread to leaf sheaths, roots and crowns during hotter, humid weather. Leaf spot is often caused by several fungi in the genera Curvularia, Bipolaris and Drechslera. It typically affects Bermuda grass and Kentucky bluegrass.

Prevention and Treatment:

One way to prevent this lawn disease is to ensure you don’t cut your grass too low. Leaf spot infections are more common in long, thick-bladed grasses. Avoid overwatering infected grass and aerate the soil to allow water drainage during rainy conditions. Adding nitrogen to the soil during a leaf spot infection can also kill an area affected by the leaf spot.

When it comes to treatment, timing matters. Systemic and contact fungicides can be used to manage infections, but remember that these products can only be applied during the initial stages of the infection. Otherwise, it will have little to no effect. It’s best to apply fungicides once in the early spring and again in late spring.

3. Dollar Spot

Dollar Spot is a common lawn disease named for the bleached to straw-colored circular spots it creates on your lawn. During the initial stages, the spot may appear as the size of a silver dollar.

As the disease progresses, the patches can merge to create large, irregular discolored spots, often several feet in diameter. Infected leaf blades will be characterized by tan bands across the blade, each showing reddish-brown margins above and below it.

The lawn fungus responsible for dollar spots primarily attacks leaf blades, not roots or soil. It thrives on warm days, cool nights, and abundant dew. Dollar spots can remain active from mid-May to mid-October, within the 60-90 °F temperature range. It tends to exhibit its most severe effects in arid soils and areas that lack nitrogen fertility.

Treatment and Prevention

To protect your lawn from dollar spots, water deeply and infrequently. Do not allow moisture stress to occur and maintain sufficient nitrogen fertility. Prune trees and shrubs regularly for better air circulation and faster turf drying.

If fungicides are needed, use them according to the manufacturer’s instructions. You can also apply fungicides preventatively during periods of high disease pressure.

4. Rust

Typical symptoms of lawn rust include yellowing grasses and tiny, spore-producing pustules that break through the leaf surface. The pustule’s color varies depending on the species of rust and the type of spore it produces. In many cases, pustules are orange in color. However, the fungus may produce black pustules containing overwintering spores in autumn. While severely infected leaves may wilt and turn brown, the disease will not usually kill the grass.

Lawns lacking in vigor due to drought stress or nutrient deficiency are more susceptible to rust. Rust commonly appears on long grass or where shrubs or trees overhang the lawn.

Treatment and Prevention

During the growing season, feed the lawn regularly to maintain vigor. Steer clear of nitrogen fertilizers in autumn as the resulting lush growth may be more prone to rust and other fungal infections. Mow periodically to minimize the number of affected leaves and prune overhanging trees and shrubs to enhance air circulation.

Symptoms of lawn rust are usually temporary, so chemical treatments may be unnecessary. Even lawns heavily infected during autumn will recover and display signs of robust growth as early as the summer of the following year.

5. Fairy Ring

Fairy rings are circular areas of abnormal turf growth that often appear on lawns where soils have high organic matter levels. They may also appear in areas where trees have recently been removed.

Fairy rings may range from a few centimeters up to several meters in diameter, with weeds commonly appearing in infested areas.

All grasses are susceptible to fairy rings. Symptoms can vary depending on the species of fungi but may include:

  • Circular or semi-circular areas of lush, dark green grass.
  • Rings of mushrooms in the affected areas.
  • Wilting or browning grass and changes in soil composition.

Treatment and Prevention:

Turfgrass growing in low fertility soils with insufficient irrigation are more likely to suffer from fairy rings. As such, regular dethatching combined with proper fertilization will help prevent the development of this disease.

If fairy rings are present, soil removal or fungicide treatment may be required to address fairy rings. Aeration and heavy watering for multiple weeks may help manage symptoms. If mushrooms appear without any zone of dark green grass, they can be raked off and disposed of, although fungicide is still required to control the infection.

EssTips to Avoid Lawn Diseases

Water Your Lawn Deeply and Infrequently

Water your lawn, preferably in the early morning. This gives the grass more time to dry before evening. Excess moisture from overwatering can only increase the risk of disease.

Mow Regularly

Avoid cutting grass too short, as this may weaken the plant and make it more vulnerable to infections. Follow the proper mowing height for each grass type.

Promote Good Airflow

Trimming or pruning shrubs and trees minimizes humidity levels. Excessive moisture buildup may create an ideal environment for fungi and diseases to thrive.

Follow a Regular Fertilization Schedule

Ensure your lawn receives the proper nutrients for healthy growth. Conversely, avoid over-fertilizing as this can also lead to disease development.

Avoid Thatch Buildup

Excessive thatch can be a breeding ground for pathogens. Dethatching your lawn prevents dead organic material from accumulating.

Aerate the Soil

Core aeration helps improve root growth, support water penetration and reduce soil compaction, which all lead to reduced risk of disease.

Monitor and Identify Early Signs

Look for any signs of disease, such as unusual patches, discoloration, or weak grasses. Early detection allows for timely treatment and reduced complications.

Let Turf Unlimited Protect Your Lawn From Disease

If you suspect that your turf is suffering from a lawn disease, the best thing you can do is consult a lawn care professional. At Turf Unlimited, we’ll diagnose the problem and come up with the right treatment approach. Contact us today and enjoy a healthy, gorgeous lawn all year.

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