The first step in dealing with a lawn disease is to diagnose the problem correctly. Close observation is essential. Brown patches that appear in a lawn may be caused by environmental factors such as drought injury, needlessly low mowing height, compacted soil, improper watering, or even dog urine. First, examine the affected turf to rule out insect problems such as sod webworms, chinch bugs or grubs.
To determine if the problem is a disease, try to pull up the damaged grass plants. Unlike insect-damaged lawns whose roots are destroyed, grass that has died from disease tends to remain attached to the soil. Exceptions include root and crown rots caused by Fusarium blight or Helminthosporium leaf spot diseases, which soften the grass so that it pulls up easily.
Each Grass Has Its Own Fungal Disease
While there is a little overlap, in most cases, each fungal disease that can hit a lawn is connected to a specific species of lawn grass, such as Tall fescue as opposed to Kentucky bluegrass. If you have a mixture of grasses in your lawn, then this fact is not important, but if your lawn is composed of just one species of grass, then this list can be helpful in your determinilng which disease is presenting a problem. The following northern grasses tend to be vulnerable just to those fungal diseases listed after each name:
Fine fescue: Dollar spot, Fusarium patch, leaf spot, powdery mildew, red thread.
Tall fescue: Brown patch, leaf spot.
Perennial ryegrass: Brown patch, dollar spot, rust, leaf spot, red thread, typhula blight.
Kentucky bluegrass: Dollar spot, fusarium blight and patch, rust, leaf spot, powdery mildew, red thread, stripe smut.
Temperatures Affect Fungal Disease
Because individual fungal diseases require certain specific environmental conditions to thrive, identification is easier. You can rule out those that do not prefer cooler or warmer temperatures.
| Temperature vs. Disease | ||
|---|---|---|
| Cool | Moderate | Warm Temperatures |
| Temperatures | Temperatures | |
| (40° to 75°F) | (60° to 80°F) | (70° to 100°F) |
| Leaf spot | Dollar spot | Brown patch |
| Melting out | Necrotic ring spot | Fusarium blight |
| Fusarium patch | Red thread | Summer patch |
| Pink snow mold | Leaf smut | Pythium blight |
| Grey snow mold | Rust | |
Stress Encourages Fungal Disease
It is important to remember that lawn diseases are often caused by an underlying environmental condition that is stressing the grass plants. A healthy lawn can defend itself against the insect pests and disease organisms that normally inhabit the lawn’s ecosystem. But when stressed, grass plants are less able to resist the disease organisms whose growth is encouraged by abnormal conditions.
Aside from extreme weather conditions, too much or too little water or fertilizer, improper mowing height, soil compaction, uneven grading, accumulated thatch, overuse of lawn pesticides, or any combination of these may stress grass plants.
Another summary to understand fungal diseases in the lawn
Dealing With Fungal Disease On The Lawn
When patches of dead grass mysteriously appear in the lawn, and you don’t own a dog, the cause will be either a pest insect or a fungal disease. You can tell the difference in most cases by pulling on the dead grass. If it comes up easily the cause is likely an insect. If it is still attached to the soil the problem is a fungal disease.
There are about a dozen fungal diseases that can mar the beauty of your lawn. You do not need to memorize the symptoms of all those diseases. When you take into consideration the season of the year (spring, summer, fall), the recent weather pattern, and the species of grass in your turf, the number of possibilities goes down to two or three diseases.
Most fungal diseases developing in the spring, will not show up in the summer or fall. Every fungal disease has a specific weather requirement for it to appear. It might want cool temperatures and low humidity, or high temperatures and low humidity. Finally, while there are a few exceptions, most fungal diseases are specific to only one or two species of grass. Diseases that hit Kentucky bluegrass are not likely to affect lawns with perennial ryegrass for example.
If you want complete descriptions of the symptoms and recommended solutions to the most common fungal diseases, go to my website www.yardener.com and in the search window type “Fungal Disease On Lawns”. You will find a quick reference chart and then detailed but easy to understand information about the fungal diseases that could invade your lawn.
Dealing With Fungal Disease
If you discover some dead patches on your lawn and you have determined that they are likely to be a fungal disease, what do you do? First you want to identify the disease, because there are different techniques used to control each disease.
Change A Lawn Care Practice – In some cases, all you have to do is raise your lawn mower to three inches, and/or dethatch the lawn, or hold back on watering. By changing the way you care for your lawn will bring the disease under control, and the lawn may even regenerate itself as a new season approaches.
Stop Doing Something – In some cases you solve the problem by avoiding certain steps. You may need to stop watering so much. You may be using too much fertilizer. You may be walking on the infected area and spreading the disease.
Use A Fungicide – Fungicides do not make dead grass come alive again., Fungicides prevent the disease from spreading further into your lawn. The sulfur based fungicides tend to work with most fungal diseases. To prevent the problem from coming back, you will not be using a fungicide, you will be changing the way you care for your lawn and hoping the same weather pattern doesn’t develop next year.
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