Lawn Disease Identification Part 1: Brown Patch

A brown patch on your lawn can be a number of things. If it’s small, it may not be very concerning and could be caused by something as simple as animal urine, mowing more than ⅓ of the blade off at one time, mowing too infrequently or mowing your grass shorter than 3-3-½”.

But there are a few more serious causes of brown patches in your lawn, and they can really become a large problem. Let’s look at a few causes and how you can battle them. If you need help, don’t be afraid to call in some extra help from Valley Green Companies; we can help keep your lawn in tip-top shape all year long.


It’s possible your brown patch could be caused by grubs. Grubs are the larvae of various types of beetles which eat the roots of grass and plants.

In order to figure out if grubs are your issue, you’ll need to cut and peel back a square foot of turf.

To get rid of grubs, you’ll need to use the proper grub control products which are most effective in the fall when they come up to feed. It’s also important to take very good care of your lawn, as grubs thrive in thin lawns with moist soil. Thick, healthy lawns will be less likely to develop this issue.


Thatch is a buildup of decaying grass blades that can build up and choke out healthy grass. A small amount of thatch is healthy, but as it builds up it becomes dangerous. A thick layer of thatch makes it hard for water to reach the soil, preventing nutrients and watch from reaching the roots of your lawn, causing the brown patch.

To find out if this is the cause, use a ruler to measure thatch levels around the brown patch. If the thatch is taller than ½”, it needs to be controlled.

To reduce the amount of thatch, lawn aeration is necessary. Lawn aeration removes soil cores from your lawn and deposits them above the thatch layer. This helps breakdown the thatch, and also creates holes in the lawn which allow water and nutrients to better penetrate the lawn. At Valley Green Companies, we utilize special aerator equipment which creates 40 holes per square foot.

Rhizoctonia Solani

Rhizoctonia solani is a fungal disease which typically appears in the summer and usually attacks perennial ryegrass, tall fescue, the bentgrasses and occasionally Kentucky bluegrass. It’s very destructive, and can appear very quickly.

With this fungus, brown patches may be from between a few inches to several feet in diameter. It’s typically active when humidity is high, night temperatures are above 68°F and daytime temperatures above 80°F.  The fungi survive the winter by hiding in heavy thatch, so lawn aeration can be a good defense to reduce thatch before winter.

Another option is the use of a fungicide, which we at Valley Green Companies have formulated just for central Minnesota lawns.

Preventing rhizoctonia solani requires a perfect blend of fertilizers; too much nitrogen released too fast increases the changes of this fungus appearing. The lawn should be provided with everything it needs to reduce stress, increasing its defense against the fungus. This can include pruning trees and shrubs to increase light and air penetration of your lawn, aeration and preventative fungicide application if necessary.

Remember, if you need help don’t be afraid to call Valley Green Companies!