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When your lawn starts to look a little funky in some spots, your first thought might be to crank up the sprinkler system and douse the spot with some fertilizer.

Put down that garden hose. If your lawn starts developing anything abnormal, it could be a sign of a bigger issue.

In the fight to keep your lawn lush and healthy, one of your biggest nemeses is lawn disease. These diseases, typically caused by different species of fungi, can wreak havoc on even the lushest of lawns if you aren’t careful. If you start to notice your lawn is looking patchy or discolored, it may be that you’ve got a lawn fungus on your hands.

What can you do if you start to notice problem spots on your lawn? Here are some of the most common lawn diseases and what you can do to treat them.

Brown Patch

Brown patch lawn disease is pretty much exactly what it sounds like. A fungus called Rhizoctonia infects your grass and causes the area to develop a circular spot of brown and dead grass. You may also notice a dark ring around the patch and tan lesions on the individual grass blades.

Brown patch thrives in areas that experience high temperatures and high humidity during the summer months. Poor soil drainage, overwatering and high nitrogen levels in the soil can also be contributing factors to the disease’s severity.

If you’ve determined your lawn has a brown patch problem, your plan of action should be to reduce the severity of the current flare up and work on prevention for next season.

When battling brown patch, continue to mow regularly, as this will promote air movement and allow your lawn to dry better. Avoid adding excess nitrogen to your lawn, and continue with your regular fertilizer schedule, being careful not to over- or under-fertilize.

Fungicides will likely prove to be fairly ineffective against brown patch that has already progressed. Instead, fungicides work best when applied as a preventive in the late spring or early summer with continued application throughout the summer months.

Summer Patch

If you notice your lawn has a bunch of irregular, straw-colored patches of wilted grass, summer patch could be the culprit.

Summer patch tends to make an appearance in the mid to late summer months when temperatures climb above 90 degrees. It’s caused by the fungus Magnaporthe poae, which infects the grass’ roots and disrupts its ability to soak up water and nutrients.  Summer patch is a highly destructive disease, and you should begin treating and managing it as soon as you notice symptoms.

Hot, humid weather creates favorable conditions for this disease to thrive. Poor air circulation and soil compaction can also contribute to its progression.

Once you’re able to see the symptoms of summer patch, the disease has already progressed, and getting it under control is difficult. To prevent summer patch from becoming an issue and damaging your lawn, apply fungicide in the late spring, when the fungus has begun doing its damage but hasn’t yet shown symptoms.

To manage summer patch, avoid excessive watering. Use a core aerator to reduce compaction and promote air circulation. Apply a fungicide to control the disease.

Dollar Spots

If your lawn is covered in many small, round, silver dollar-sized brown spots, you’re likely dealing with dollar spot fungus.

Dollar spot tends to appear from late spring to late fall, and prefers warmer temperatures and lots of humidity.

Be sure you’re following an appropriate fertilizing schedule for your lawn, as this disease tends to be more prevalent on under-fertilized grass. Excess moisture and mowing too short can also encourage the progression of dollar spot.

To treat dollar spot, continue to follow your fertilizer schedule, as proper fertilization will help your lawn outgrow the disease. Water deeply but infrequently so that water can penetrate to the roots but will be less likely to linger and create moist conditions, which are ideal for fungal development. Aerating your lawn will also help the moisture penetrate while introducing air flow.

Red Thread

If you’ve got red thread, blame Laetisaria fuciformis. Red thread is pretty distinctive and shows up in your yard as tan or reddish spots. Upon closer inspection, you’ll notice pink, thread-like structures growing from the tips of the infected blades of grass.

Red thread can develop within a relatively wide range of temperatures, usually in the spring and fall. It thrives in cool, wet conditions with limited sunlight. It’s more common in areas with a lot of rainfall.

The key to preventing red thread is to ensure you’re adequately fertilizing your lawn, as undernourished grass is more susceptible to infection.

To treat a current infection, keep up with your regular lawn care, and make sure you’re supplementing your soil with the proper amount of nitrogen.

Red thread generally isn’t a big threat to the health of your lawn and is more of a cosmetic concern, so it doesn’t require a large amount of intervention beyond ensuring that you’re properly nourishing your grass and soil and providing your lawn with enough nitrogen. As such, it may take several seasons before you’re able to get your soil balanced enough to prevent red thread from recurring.

Powdery Mildew

If your lawn looks like a baker sprinkled parts of it with some flour, you’re likely dealing with Erysiphe graminis, the fungus behind powdery mildew.

Powdery mildew likes shady areas in cool, humid climates. Because of this, it’s more common in the spring and fall.

Powdery mildew can damage your grass and, if left untreated, can cause thinning in your yard. To manage the disease, do what you can to increase the amount of sunlight the affected areas of your yard get, such as pruning trees and shrubs. If the grass is in a permanently shaded area you may consider removing the grass and putting down mulch instead in that particular area.

Applications of fungicide may help prevent the growth of powdery mildew.


Is your yard looking a little rusty? No, it’s not the same rust that you see on an old car. Rust fungus is an organism that can infect your grass and give it the appearance of rusted metal. If you think your yard has a rust fungus infection, inspect the grass for small, yellow flecks on the individual blades.

As this disease progresses, the small yellow spots will enlarge and release powdery orange spores.

Rust prefers moderately warm temperatures and lots of humidity. Low nitrogen levels in the soil can also be a factor.

Preventative fungicide application can be used to inhibit future growth. To treat the disease, continue to mow regularly (but not too low) and avoid overwatering. Prune nearby landscaping to maximize light exposure and airflow. Consider planting rust-resistant grass seeds.


Your best defense against lawn diseases is a good lawn care plan. How you care for your lawn will depend on the specific type of grass you have growing in your yard and the makeup of its soil. Here are some basics that will help you put your best foot forward in the fight against fungus.

A good first step is knowing what type of grass is in your yard. There are many different varieties throughout the U.S., and knowing which type you’re caring for will help you make the best decisions on how to care for it.

You should also become familiar with your local county extension office, which can help you when you have any questions about gardening, agriculture and pest control. They’ll give you useful information specific to your location. They can also test samples of your soil and give you recommendations on what types of treatments you should be applying to it.

Once you know what type of grass you have and what the growing environment in your area is like, you’ll be able to create an appropriate fertilizer schedule and know what length to cut your grass.

Water your lawn early in the day so it has time to dry with the help of the sun. Once it gets dark, water won’t evaporate as well and will remain in the soil, encouraging infection.

Remember, fungicides work best as a preventative. If you’re currently having problems with lawn disease, make a note of that for next year, and start applying a fungicide in the spring, so problems can’t recur.

Do you have any tips to keep your lawn fungus-free? Share them in the comments!

This Post Has 4 Comments

    1. Hi Dot:

      We aren’t experts in particular fungicides, but you could probably get advice on what works best for a particular problem at your local home and garden supply store.

    1. Hi Radu:

      That’s good feedback that we can absolutely take into account moving forward.


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