How to avoid 3 summer lawn diseases

Updated Jun 8, 2023

All lawn diseases have their peak seasons, and some in particular are more prone to show during the summer months. Here are three to look for as the weather warms up.

RustOnLawns-big1. Lawn Rust
What is it?
Lawn rust typically occurs during the summer and early fall months and is caused by a lack of nitrogen in the soil.

How can I identify it?
Look for an overall lawn appearance of yellow, brown, or red. Examine the grass carefully and pick-up a few blades. The spore residue from rust has a tendency to rub off when touched.

turf-rust-bigWhat causes it?
Lawn rust is the result of inadequate nitrogen and moisture in the soil. Most likely, you haven’t been watering deeply or frequently enough, or you might be cutting the grass too short. Heavy rainfall and sudden changes in humidity can also contribute lower nitrogen levels. And lawn rust is easily spread by people, lawn equipment, wind and rain.

How can I solve it?
Don’t mow as often, and adjust the blade height of your lawn mower to the highest possible setting. Never trim off more than one-third of the grass length when mowing. Water your client’s lawn with about an inch of water per week and apply a low-nitrogen fertilizer to the lawn. Normally, rust will fade away by early fall. Most cases will not need the application of any type of fungicide for control or prevention.

Photo credit: University of Minnesota Extension

Iowa State University Extension and OutreachIowa State University Extension and Outreach

2. Powdery mildew
What is it?
Powdery mildew occurs in shady spots on the landscaping. The issue is more predominant in northern states in the United States and occurs from spring until early fall. While it can be a huge nuisance, the good news is that it is also fairly easy to recognize and treat once discovered.

How do I identify it?
You’ll be able to spot powdery mildew in the spring after the disease survives the winter and spreads through spores at the beginning of the spring season. Identify powdery mildew by looking at the texture of leaves on the lawn. The disease shows itself by creating a felt-like surface on leaves. Powdery mildew gets its name from the gray-white dust that forms on the leaf’s surface.

What causes it?
The problem spreads the most in shady areas (which most often are less maintained than other areas of the lawn). It most commonly occurs in bentgrass, Bermuda grass, fine fescue, Kentucky bluegrass and ryegrass. The disease thrives on low sunlight and cooler temperatures, making shady areas the prime location for damage.

How can I solve it?
If your customer’s lawn contains any cool and shady areas, try to bring in more sunlight. Prune trees to minimize their coverage of the grass. Use a deep watering plan to ensure that the soil has adequate moisture. In this case, deep watering is more effective than frequent shallow watering. Unfortunately, in some cases, chemical control techniques are necessary to eliminate the problem and prevent it from returning.

Symptoms of dollar spot disease on creeping bentgrass putting green, via Penn State College of Agricultural SciencesSymptoms of dollar spot disease on creeping bentgrass putting green, via Penn State College of Agricultural Sciences

3. Dollar spot
What is it?
Dollar spot is caused by Sclerotinia homoeocarpa, a fungal pathogen. It does not affect the roots or crown of the grass in the lawn, but it can cause unsightly brown spots on the leaf tissues of the grass, negatively affecting turf vigor and appearance. Dollar spot typically shows up in late spring and early summer.

How to identify it?
If you think your client may have dollar spot, look for outbreaks of round, tan-colored spots in clusters. These spots can be up to 1 inch in diameter. Look at individual leaves of grass. If they have dollar spot disease on their lawn, you will notice lesions on the blades that appear straw-colored in the middle, with red-brown outlines around each lesion.

What causes it?
Dollar spot disease is often caused by a lack of nitrogen in the soil where grass has been planted. Normally, depletion of nitrogen occurs in late spring or early summer, which helps the disease spread faster. Mycelial, the pathogen that causes this disease in part, also becomes active in the springtime. Extended dew periods of around eight hours or more and temperatures between 55 and 80 degrees Fahrenheit help mycelial grow and become more active. The disease can also be spread by the use of infected blades during mowing, core aeration, or other lawn care operations.

How can I solve it?
There are quite a few options for control of Dollar spot disease. You should begin by planting cultivars of grass that are less susceptible to the disease. To help control the disease, switch irrigation to a nighttime and early morning schedule so as not to contribute to longer dew periods. Also, be sure to keep the soil rich in nitrogen by applying fertilizer mid-summer. And as usual, keep the grass trimmed to a height of 2 to 3 inches.

Fungicides may also be applied to the lawn if the above treatment methods don’t work if you have an especially severe outbreak of the disease on the lawn, or if you need quick results.

About the Author: Philip Brown is a lover of green, healthy lawns. A former TruGreen lawn care professional, Philip now spends his time sharing what he knows with others and blogging about it at The Lawn Enthusiast. Connect with him over on Google+.

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