Beware of Central Ohio Lawn Diseases

Besides turf-damaging insects, lawn diseases can also cause problems. Lawn diseases are usually the result of a combination of factors coming together at the same time to allow the disease to take hold of the turf-grass plant. Although treatment for lawn diseases is possible, it is not always advised as many turf diseases will correct themselves as soon as conditions improve.

Lawn diseases are most often the result of the right conditions combining with the right time of year. Usually a lawn disease does not need to be treated (there are a few exceptions) but the conditions causing the disease should be addressed as soon as possible.


Snowmold is most common to Kentucky Bluegrass and Fescues. Appears more often when we’ve had a winter when snow remains on the lawn for an extended period of time.

The best prevention for snowmold is to aerate often. Improving water drainage, raking leaves off lawn’s surface, and follow a fertilization schedule to help prevent over-fertilization in the late-fall can also help.

Dollar Spot

Dollar spot is common to closely cut Kentucky Bluegrass during humid weather conditions. The disease gets its name from the small silver dollar-like shapes. Usually looks brown or straw-colored in appearance. The spots may merge to form large patches several feet wide

Dollar spot is most common during warm, wet weather with heavy dews and in those lawns with low levels of nitrogen.

Water only in the morning hours if additional water is necessary, remove excess thatch, and follow a fertilization schedule.

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.

The best prevention for fairy ring is to aerate the diseased area, water in the morning hours, remove excess thatch, and follow a regular fertilization schedule.


Rust gets its name from the orange, “rusty” appearance it gives leaf blades. Most commonly effecting ryegrasses and Kentucky Bluegrass, rust tends to flourish in conditions of: morning dew, shade, high soil compaction, and low-fertility. The best way to check for rust problems is by taking a white tissue or paper towel and rubbing a few grass blades through it. If an orange color remains, then it’s usually rust.

The best prevention for rust is to aerate your lawn, water well in the morning hours, reduce shade to grass, mow more frequently and bag grass clippings during those times when rust is most likely to form. Follow a fertilization schedule to help increase the amount of nitrogen levels in your lawn.

If Rust has been a problem in the past, mow frequently and remove clippings from lawn.

Grease Spot / Pythium Blight

Grease Spot, better known as Pythium blight, can effect all grasses in humid climates and can be recognized by the slimy-brown patches that often have a white, cotton-like fungus around it. Grease Spot gets its name for the “greasy” appearance it makes while matting together and can appear in streaks across the lawn.

The best prevention for Grease Spot is to aerate often, water in the morning hours only, remove excess thatch, reduce shade on lawn, and cutback on the nitrogen levels during fertilization.

Red Thread
(Laestisaria Fuciformis)

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.

It attacks only leaves and leaf sheaths and is seldom serious enough to kill a lawn.

The red treads will be most visible when wet.

The best prevention for Red Thread is aerate often and remove thatch. Mowing to proper levels, reduce shade on lawn, follow a regular fertilization schedule. Make sure to include nitrogen and potassium.

Powdery Mildew

Grass looks as though it is sprinkled with flour. Kentucky bluegrass and shade areas are the most susceptible. Grass will wither and die.

Water only in the morning; reduce shade by pruning, aerate and check drainage in the area.

Pythium Blight

Irregularly shaded spots of wilted brown grass. Cobweb-like mass of fungus on moist nights or mornings. Patches cluster to form streaks a foot or more wide

Do not over fertilize or over water and don’t mow when grass is wet.

Fusarium Blight (Summer Patch)

Light green patches that spread, turn reddish brown and then die.

Apply a fungicide in late spring. Do not over fertilize and maintain a good watering schedule.

Leafspot-Melting Out

Brown to purple lesions (spots on blades. Irregular dying areas of grass lesions on grass in margins of dead area. Caused by excess nitrogen fertility and possibly excess thatch buildup

Do not introduce additional nitrogen when fertilizing, aerate and detach lawn.

Slime Mold


Like powdery mildew, slime molds covers grass with a powdery covering that looks almost like crystallized frost. Feeds on decaying organic matter found in the soil. As the powdery covering becomes thicker, it reduces the light reaching the plant cells, and they begin to turn yellow.

No prevention. Usually not harmful.

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