Many times, people discover a brown spot in their lawn and jump to the conclusion that the lawn has a disease. Fungal diseases of lawns are actually quite rare in Nevada. Many things can cause brown spots in lawns.

 

Your irrigation system. Sure, you see the sprinklers come on, but are they watering properly and evenly? One of the most common causes of brown spots in lawns is lack of water or uneven water distribution. Check your sprinkler system regularly and adjust the amount of water as then weather changes. Do a test to see if the sprinklers deliver the same amount of water everywhere. If not, adjust the system to improve it.

 

A brown spot caused by uneven watering.

 

Accidentally mowing too short or “scalping” your lawn can result in brown spots.

 

Does your neighbor? Dog urine can cause brown spots, especially if the site is used regularly. If you catch a dog “watering” your lawn, flush the spot with water as soon as possible.

 

Animals such as rabbits, marmots and ground squirrels can cause brown spots by overgrazing your grass. Applying a fungicide will not control these animal pests or solve the problem.

 

W. Hanson Mazet, UNCE
This cottontail has eaten the grass down to the soil surface, leaving a brown spot.

 

Brown spots in lawns can result from soil compaction or thatch. To check for it, try to push a screwdriver into the brown patch after the sprinklers have watered the area. If you can’t push the screwdriver in but the ground is wet, you may have a compaction or thatch problem.

Next, dig a hole. If you have a compaction problem, you will see soil with few plant roots growing in it. If you have a thatch problem, you will

see a thick layer of grass roots and stems with very little soil mixed in. You can improve both compaction and thatch by core aerating and top

dressing with compost. Do not add more than one-quarter inch of compost at a time to an existing lawn. Rake the compost into the holes made by the core aerator. You may have to do this several times over the course of a couple of years to see improvement.

 

Thatch is the spongy layer of roots and stems. W. Hanson Mazet, UNCE

 

 Use a screwdriver to test for compaction and thatch. W. Hanson Mazet, UNCE

This is a fungal disease that occurs in our area. Fairy ring forms a brown circle or semicircle that is often surrounded by a dark green circle or semicircle of grass. The brown ring will be very dry and may show whitish to grayish mycelium (powdery or stringy fungi) in the soil below.

The dark green circle may or may not have mushrooms growing in it. Fungicides are not very effective in treating fairy ring. Fairy ring forms most commonly when organic debris, such as dead or dying tree roots or scrap wood, was buried in the lawn area. If you have a chronic

problem, try digging up the sod. Something buried underneath may be causing the problem.

 

Fairy ring, shown above, results in a typical yellow or brown ring. W. M. Brown Jr., Bugwood.org

 

Many things can cause brown spots in lawns. Check for the cause of the brown spots in your lawn before you buy a pesticide.

 

 

• Adjust your irrigation system so it waters the same amount everywhere.
• Check your irrigation system regularly throughout the season.
• Train your dog not to relieve itself on your lawn.
• Fence out rabbits and other critters that feed on your lawn.
• Aerate your lawn and remove excess thatch. Top dressing with compost will also help.
• Sharpen mower blades and mow high. Mowing too short or with dull lawn mower blades can cause brown spots in your lawn.
• Apply the right amount of fertilizer on your lawn. Too much fertilizer can “burn” your lawn, causing brown spots.

University of Nevada, Reno Extension

The above information is based on a printed factsheet (What is that Brown Spot in my Lawn) originally published in 2012. 

 

Many times, people discover a brown spot in their lawn and jump to the conclusion that the lawn has a disease. Fungal diseases of lawns are actually quite rare in Nevada. Many things can cause brown spots in lawns.

 

Your irrigation system. Sure, you see the sprinklers come on, but are they watering properly and evenly? One of the most common causes of brown spots in lawns is lack of water or uneven water distribution. Check your sprinkler system regularly and adjust the amount of water as then weather changes. Do a test to see if the sprinklers deliver the same amount of water everywhere. If not, adjust the system to improve it.

 

A brown spot caused by uneven watering.

 

Accidentally mowing too short or “scalping” your lawn can result in brown spots.

 

Does your neighbor? Dog urine can cause brown spots, especially if the site is used regularly. If you catch a dog “watering” your lawn, flush the spot with water as soon as possible.

 

Animals such as rabbits, marmots and ground squirrels can cause brown spots by overgrazing your grass. Applying a fungicide will not control these animal pests or solve the problem.

 

W. Hanson Mazet, UNCE
This cottontail has eaten the grass down to the soil surface, leaving a brown spot.

 

Brown spots in lawns can result from soil compaction or thatch. To check for it, try to push a screwdriver into the brown patch after the sprinklers have watered the area. If you can’t push the screwdriver in but the ground is wet, you may have a compaction or thatch problem.

Next, dig a hole. If you have a compaction problem, you will see soil with few plant roots growing in it. If you have a thatch problem, you will

see a thick layer of grass roots and stems with very little soil mixed in. You can improve both compaction and thatch by core aerating and top

dressing with compost. Do not add more than one-quarter inch of compost at a time to an existing lawn. Rake the compost into the holes made by the core aerator. You may have to do this several times over the course of a couple of years to see improvement.

 

Thatch is the spongy layer of roots and stems. W. Hanson Mazet, UNCE

 

 Use a screwdriver to test for compaction and thatch. W. Hanson Mazet, UNCE

This is a fungal disease that occurs in our area. Fairy ring forms a brown circle or semicircle that is often surrounded by a dark green circle or semicircle of grass. The brown ring will be very dry and may show whitish to grayish mycelium (powdery or stringy fungi) in the soil below.

The dark green circle may or may not have mushrooms growing in it. Fungicides are not very effective in treating fairy ring. Fairy ring forms most commonly when organic debris, such as dead or dying tree roots or scrap wood, was buried in the lawn area. If you have a chronic

problem, try digging up the sod. Something buried underneath may be causing the problem.

 

Fairy ring, shown above, results in a typical yellow or brown ring. W. M. Brown Jr., Bugwood.org

 

Many things can cause brown spots in lawns. Check for the cause of the brown spots in your lawn before you buy a pesticide.

 

 

• Adjust your irrigation system so it waters the same amount everywhere.
• Check your irrigation system regularly throughout the season.
• Train your dog not to relieve itself on your lawn.
• Fence out rabbits and other critters that feed on your lawn.
• Aerate your lawn and remove excess thatch. Top dressing with compost will also help.
• Sharpen mower blades and mow high. Mowing too short or with dull lawn mower blades can cause brown spots in your lawn.
• Apply the right amount of fertilizer on your lawn. Too much fertilizer can “burn” your lawn, causing brown spots.

University of Nevada, Reno Extension

The above information is based on a printed factsheet (What is that Brown Spot in my Lawn) originally published in 2012.