Types of Patch Disease

Lawn maintenance is needed to prevent diseases from ruining one's property. Patch disease commonly affects turf grass. Thatch, poor soil quality, improper sod installation, and overuse of nitrogen are factors that can contribute to this type of lawn disease. If you've installed a sod lawn in the past 2 to 5 years over clay soil, you may also be at risk for this destructive disease. However, distinguishing between the various types of patch disease can help you choose the most effective form of treatment.

Type of Patch Disease

Rhizoctonia Yellow Patch: This type of patch disease, also known as Rhizoctonia cerealis, typically affects Kentucky bluegrass. Since yellow patch is brought on by wet, cool seasons, it seeks out newly laid sod that has been applied on heavy soils. Yellow patch also overruns lawns that have compacted soil or excessive thatch.

Properties suffering from yellow patch usually have light green or yellow green patches. These patches will change color after a short time, causing them turn either light tan or brown. In addition to changing colors, the affected areas may also grow taller. The "frog-eye" symptom is associated with this type of patch disease, exposing green centers in the yellow green to brown patches. Thatch that's decomposing may cause the patches to appear lower than other lawn areas. Yellow patch can lead to further discoloration near the borders of the affected area. Leaf blades may appear reddish or reddish purple. Before the blight completely takes over, leaf blades may have tan spots featuring dark edges.

Unlike other types of patch disease, yellow patch does not result in black strands of fungus on leaf blades. Since this type of disease is caused by cooler conditions, you can lower your lawn's risk for yellow patch by aerating the lawn before it has been laid on heavy soil. It's important to note that fungicides do not fend off yellow patch.

Summer Patch: Indicative of its name, summer patch is the most prevalent during the summer. This type of patch disease is caused by the fungus Magnaporthe poae. Summer patch is especially harmful to turf, causing it to yellow. Over time, these yellow patches will thin before bronzing. If the hot weather persists, all the turf in the affected area can die. This makes it easier for intrusive weeds to take over.

Since summer months can lead to drought, it's important to prevent the soil from drying out. Watering and an irrigation system can stop this patch disease from occurring; however, excessive watering or irrigation can make the problem more serious.

Rhizoctonia Blight: This disease used to be referred to as brown patch. Similar to summer patch, Rhizoctonia blight is sparked by warm temperatures. Circular rings are a common characteristic of this disease. In fact, these rings display a dark gray or dark purple outer ring during a humid morning; however, these "smoky" rings fade during the afternoon. This disease-ridden grass will appear dark before it dries out into a light brown.

Rhizocotonia blight is most likely to occur when the temperature is between 80 and 90 degrees; however, the disease can develop during summer nights when the temperature is above 70, or if there's a prolonged dew period.

In addition to warm temperatures, this type of patch disease can also be caused by overusing nitrogen-rich fertilizer. To protect your lawn from Rhizoctonia blight, it's important to remove excess thatch and limit the amount of fertilizer being used.

Fusarium Patch: Fusarium patch thrives under a blanket of snow, covering ground that is not frozen. Once the snow melts, yellow patches will appear. Wet conditions, like melted snow, may also stimulate mold growth. In addition to wintry conditions, this patch disease can also develop during the fall and spring. This is because the weather is cool and wet. If these conditions remain, these patches will continue to grow. After a while, these patches will look as if they've been bleached. Regular maintenance, including mowing and proper fertilization, can prevent Fusarium patch. Using fungicide is an alternative; however, it's not generally recommended.

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