Lawn Disease and Fungus

Lawn diseases are a growing problem and hard to decipher, but figuring out what symptoms your lawn is showing will help you and your lawn care professional diagnose the problem and find the cure!

Although there are over 70 diseases of turf grass species worldwide, Midwestern lawns are usually only affected by few. We deal with some very extreme weather, and knowing what works best for your specific lawn is exactly what we hope to help with.

Most lawn diseases are caused by a fungus that lives off of your grass. They show up as spots, circles, dry patches in colors that range from yellow, brown or red. Properly diagnosing the problem and finding the cure is what we aim to do.
Here are some of the most common lawn diseases and treatments for them:

Snow Mold:

There are two types of snow mold, gray and pink. They are caused by different pathogens but often occur under the same environmental conditions.

Gray snow mold is first noticeable in early spring after the snow melts. It usually shows up in areas where snow has accumulated for long periods of time (i.e. along driveways and in areas where snow drifts develop). Grass that has been affected by gray snow mold has a matted, bleached, gray look to it. In most cases, infected grass blades are killed, but crowns and roots usually survive.

Pink snow mold does not need the accumulation of snow. It can show up in the moist weather in spring and fall. The fungus is will show up on the grass blades with a pink hue on the affected areas. The affected grass becomes brown or tan as warm dry weather returns. Like gray snow mold, pink snow mold usually kills leaf blades only. However, if left untreated the pink snow mold can damage the root system.

Snow mold problems can be minimized by mowing your lawn at the recommended heights well into the fall to avoid the exposure of extra long grass, which bread disease. Eliminating snow piles in problem areas will help reduce the snow mold threat. Also, improving drainage to eliminate accumulating moisture, and lightly raking affected areas in the spring to break up and dry out the matted grass. Aeration and over seeding may be necessary if infected areas do not recover.

Brown Patch:

Brown Patch is most common to Bermuda, Kentucky Bluegrass, Centipede Grass, Bent Grass, St. Augustine, and ryegrasses in areas with high humidity and/or shade.

Brown patch lawn disease attacks many types of grass and really feeds off lawns that receive a large amount of fast release nitrogen fertilizer. It is usually seen in the summer and is caused by a fungus called Rhizoctonia. The disease begins to show when temperatures hit 65 degrees, but then grow more actively when temperatures rise into the 80’s and becomes more humid.

Once started, brown patch lawn disease spreads fast. Brown patch damage first appears as circular areas of brown and dead grass surrounded by a narrow, dark ring. Brown patch lawn disease grows out from a central point, so these circular areas can enlarge rapidly. Brown patch circles range from a few inches in diameter to several feet, and are not always true circles. Sometimes the patches grow together, creating large irregular dead areas with a sunken effect.

Since high levels of fast release nitrogen increase disease activity, it is imperative to use the correct blend of fertilizers for lawn fertilizing during the warmer months. To reduce stress on the lawn, always keep it cut at least 2 inches long, especially in extreme periods of hot and humid weather. If possible, increase light and air by pruning overhanging trees and shrubs. During cooler seasons, a core aeration will help strengthen the root system and allow new, healthy grass to grow in the infected areas.

Dollar Spots:

Dollar spots are most common to Kentucky Bluegrass, Bent Grass, and Bermuda in humid climates. They get their name from their small silver dollar-like shape and usually look brown or straw-colored in appearance. Dollar spots tend to thrive during drought conditions with heavy dews and in those lawns with low levels of nitrogen.

The fungus usually lies dormant in the winter and then as temperatures rise, so do the brown spots. Dollar spots seem to develop on all types of grasses. They are small, distinct circles from 1 to 6” across, about the size of a small pancake. Because these spots don’t look very serious individually, it’s easy to underestimate the damage potential. However, dollar spot lawn disease kills the turf clear to the roots and serious scarring of the lawn can occur.

This disease seems to feed off low nitrogen and low moisture. It’s helpful to water your lawn regularly in the early morning hours so moisture doesn’t set overnight. A low nitrogen fertilizer should be applied along with aeration and seeding to allow new healthy growth.

Fairy Rings:

Fairy Rings can grow in most grasses, and are distinguishable by circular rings filled with fast-growing, dark-green grass. Around the perimeter of the ring, the grass will typically turn brown and often times grow mushrooms. Fairy rings typically grow in soils that contain wood debris and/or old decaying tree stumps.

Fairy rings are caused by various species of fungi that inhabit most Midwestern soils and obtain their nutrients from dead and decaying organic matter. Their activity is most noticeable during spring and fall, especially when turf is under conditions of environmental stress, particularly moisture stress and nitrogen deficiency. The rings can enlarge from a few inches to several feet in diameter each year. Sometimes the rings grow together, giving them a scalloped, rather than a ring appearance. Fairy rings are classified according to 3 types based on their symptoms. Type I rings are identified by a ring of dead grass, sometimes with an additional ring of dark green grass. Type II rings are characterized by a ring of lush, dark green grass that appears to be growing faster than other turf. Type III rings exhibit only a ring of mushrooms.

Regardless of their which type they are, fairy rings are impossible to eliminate. They are best managed by alleviating stress to reduce their prominence and disguise their appearance.

Having your lawn aerated and deep watering will reduce the extent to which they develop. More frequent mowing and the application of moderate amounts of nitrogen fertilizer will help mask their appearance too.

Red Thread:

Red thread is most common to Fescues, Ryegrasses, and Kentucky Bluegrasses during times of moist and cool weather. Red Thread gets its name from the pinkish-red threads that form around the leaf blades and bind them together. Eventually, the affected grass will turn brown and the red treads will be most visible when wet.

The symptoms of red thread lawn disease first appear as “water soaked” darkened irregular areas from just a few inches to several feet across. These areas gradually become bleached or tan colored. Healthy plants are usually interspersed with diseased plants, giving the lawn an over-all ragged look.
As the red thread becomes well developed, light pink to red fungus strands (or threads) 1/4” or more in length begin to grow from the tips of the blades and the leaf sheaths — these threads are the reason for the disease’s common name. The wind moves bits of these threads to non-infected plants to spread the disease. The threads can also touch nearby blades to spread the infection. Red thread lawn disease very seldom wipes out an entire stand of turf, and so infected lawns will often have an uneven or patchy appearance.

Lawn treatments with fungicides are usually effective, mowing your lawn about 2”, reducing shade on the lawn and having your lawn aerated will help fight this disease.