Brown Patches in Lawn: Causes, Identification, and Prevention

Apparently, no one wants their beautiful green stretch of grass filled up with patches of brown, dead grass – which is officially called “brown patch”. If there is no timely action to prevent these brown spots, it will light up an alarming and frustrating situation ruining your lush green lawn. Brown patch in lawn is a disease condition caused by many different reasons. Therefore, in order to get rid of this problem, you’ll need to determine the common causes to treat and prevent brown spots in the right way.

Below are multiple causes of brown patches in the lawn and how to repair and prevent them to get back to your entire lawn.

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Fungus is the most common cause causing brown spots with irregular patches, usually the fungus Rhizoctonia. Brown patches are summer lawn diseases when the daytime temperatures reach 65 to 85 degrees. Fungal diseases often cause patches of dead grass from mid-to-late summer – when there is hot and humid weather, or even spring (when the snow melted).


Severe rainy or humid weather along with poor air circulation and the lack of sunlight will encourage an ideal condition for fungal outbreaks. If the brown patch disease is active for a long time in the lawn, it will leave a ring of dead grass around the patch, and luckily, the grass inside can recover.

ring of dead grass

There are several reasons for brown patch fungus in addition to hot and humid conditions. Excessive nitrogen (or low level), poor soil, lack of fertilizer and air movement, too much thatch, and compacted soil are also factors that promote a fungus problem. Although you cannot control the weather, there are some steps you can take to protect lawns against fungus.

Aeration and dethatching in the spring are two first efforts in preventing fungus. Proper watering, maintaining nitrogen levels at the optimal or applying fungicide all help control the fungal growth.


Grubs often appear underground in most lawns from mid to late summer and cause brown patches by damaging the root system. You could identify grubs and larvae by pulling a small area of turf which is brown patches and around dead grass areas. Pest-infested grass is much more easily pulled up than others since the root is damaged.

The feeding habit of grubs can lead to a uniform area of brown spots in your grass. There are some grub control products available to kill existing grubs, like beneficial nematodes or milky spore, etc.


Thatch is the build-up of organic material and dead debris accumulating between the root system and grass blades. Usually, your grass garden will need a layer of thatch to protect the lawn against the attack of outside factors like extreme temperatures. Excessive thatch, however, can choke the lawn by restricting the airflow, nutrients, and water absorption to roots.

half an inch layer of thatch

Once you notice there is a layer of more than a half of thatch build-up, grassroots start growing in the thatch layer, instead of soil. They can not absorb water and nutrients, therefore, the grass begins to dry out and turn brown, causing dead spots onto your healthy lawn and making your grass garden susceptible to pests and diseases.

You absolutely fix brown spots by using a dethatching rake to dethatch or aerate the lawn. But remember the most ideal time to dethatch the excessive thatch layer is not when you notice the brown patch but the most active growing season of grass. And make sure to purchase the rake which is appropriate for your grass type.


Important factors in mowing the grass lawn include the height and frequency of mowing. In case your lawn is infrequent of being mowed, it requires a deeper cut to reach a proper height. However, if your mower blades are sharp and you begin to cut your grass too short, it can cause stress on the lawn ground and create some brown spots. Always remember to keep your mower blades cut no more than a third of the grass blades.


Overwatering and underwatering are both common causes of brown patch disease. While underwatering creates a drought condition for soil, too much watering can lead to saturated soil conditions. Although most grass can tolerate drought conditions for a while, they will leave brown spots onto the ground, or even die through extended periods of high temperatures in late summer.

However, overwatering will suffocate the grass and weak the roots. Ideally, lawns need watering averaging one inch of water per week, including either rainfall or irrigation.

over fertilization

Besides, over-fertilization will leave your lawn excessive nitrogen that causes unwanted brown spots. There is a recommendation of professional lawn care not to add fertilizer on hot days to easily do weed control.

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Mostly, your lawn health depends on the quality of the soil condition. Poor soil quality, such as lack of nutrients or compacted soil, can lead to brown patches and weakened root systems. This issue can make your lawn vulnerable to pests and insects. Also, pH levels might be not optimal for your lawns, so check the soil condition and take the next approach to aerate the grass.


Dog urine, or other animals like birds, can create brown spots on your lawn since it contains a high amount of nitrogen. Brown spots due to urine burns could be recognized by brown centers surrounded by dark green rings. The best way to solve this problem is to rake the ground and cover it with topsoil and spread seed.


Your lawn could be made up of different types of grasses. While cool-season lawns go dormant during the hot weather, some warm-season grasses will go dormant in the winter. Grass will turn brown when it goes dormant. And that’s why you’ll have some brown patches of dormant grasses whereas others stay green.

brown spots on lawn mixture of dormant grass and green one


Apply Fungicide

Some experts in the lawn care field advise that most lawns could recover themselves without chemical intervention, and fungicide treatment is only appropriate for some high-value ryegrass. However, in some cases, you should use chemicals for some brown patch fungus. Different types of chemical treatments will show the results at different times.


The first spray of fungicide should be spread right after the first sign of brown spot. Although homeowners can purchase and use chemicals onto their lawn, it’s better to have professionals finish this job since they are trained to diagnose and know how to treat lawn disease in the right ways.

Water Properly

Excessive moisture causes brown patch conditions, so do not allow your lawn maintain wet all night. Make sure to water your lawns between 4 PM to 6 PM, or in the morning. And ensure the lawn should be dried out before nightfall comes.

Improve Air Circulation

One more way to cure your lawn disease is to improve air circulation which will reduce humidity and prevent fungus. Two approaches you should use are to aerate and dethatch annually.

Dethatching can be done with a dethatching rake or power equipment to remove a layer of organic material. The equipment is available at tool rental outlets. The aeration process is normally done with a core aerator, or you can hire a professional lawn care service.

Reseed Lawn with Resistant Grass Seeds

If all efforts you’ve put in failed, try to reseed with seeds that are resistant to fungus. When you notice brown patch occurrence on your lawn, consider seeding lawn with moderate resistant grasses to the Rhizoctonia fungus. You can check the types of grasses on your local extension service for some recommendations.

Don’t hesitate to contact Green Arbor Landscaping now!

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