Lawn diseases are a good indication that your landscape might be out of balance

Sometimes bad things happen even to the healthiest lawns. Lawn Diseases are one of those things. However, lawn diseases are often a sign that the lawn is under stress and this stress is allowing the disease to become a problem. It is important to find out what is causing the stress before trying to fix the disease with a prescription.

Lawn diseases are enough to perplex all of us to no end. Many lawn diseases are not easy to identify and to distinguish from other problems such as pests or poor maintenance. Ask anyone who has encountered lawn diseases and they will tell you how frustrating they can be. Much like human diseases, lawn diseases can be difficult to properly diagnose and even harder to treat correctly. Fear not, we have some tips to help you identify and treat your lawn problems.

Chances are that some of you reading this will already have a lawn disease problem. If so, the most common controls is to use a fungicide on your lawn. Various types of fungicides exist, so make sure that you use the right one. Some of the broad-spectrum fungicides will not only treat your disease, but can kill-off other good organisms and insects as well—not good! Since most lawn diseases are identified in spots before they spread, it's a good idea when using fungicides to first try to spot treat these areas to minimize the damage a fungicide can cause to your lawn's ecosystem.

As always, follow the instructions listed for each fungicide to help prevent possible damage to the environment and illnesses that can be caused by its use.


Diseases can form a resistance to fungicides after repeated use. Try to minimize this through using various types of fungicides.

There are three types of fungicides available.

  1. CONTACT FUNGICIDES: once applied, remain on the plant's surface and kill spores that come in contact with it.

  2. SYSTEMIC FUNGICIDES: applied to the leaves and then moves throughout the plants circulation system including its roots. Has a longer residual life span than contact types.

  3. PENETRANT FUNGICIDES: similar to Systemic types, but act as a preventative treatment to stop the growth of pathogens.

Best cure is an ounce or two of prevention

The best prevention though is maintaining healthy turf, be careful of over-watering, or watering at the wrong time of day (see watering info). Here then are a list of common lawn diseases and what can be done to prevent future infections.






Snowmold is most common to Kentucky Bluegrass and Fescues in regions where snow falls and sits on the lawn for extended periods 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.

The most common fungicide used on Snowmold is benomyl.

Brown Patch

Brown Patch is most common to Bermuda, Kentucky Bluegrass, Centipede Grass, Bent Grass, St. Augustine, and ryegrasses in regions with high humidity and/or shade. Brown patch commonly starts as a small spot and can quickly spread outwards in a circular or horseshoe pattern up to a couple of feet wide. Often times, while expanding outwards, the inside of the circle will recover, leaving the brown areas resembling a smoke-ring.

The best prevention for brown patch is to aerate often, reduce shade to effected areas, and follow a fertilization schedule to help prevent fertilization with excess amounts of nitrogen.

The most common fungicides used on Brown Patch are: benomyl, and chlorothalonil.

Dollar Spot

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 best prevention for brown patch is aerate often, water well in the morning hours, remove excess thatch, and follow a fertilization schedule to help increase the amount of nitrogen levels in your lawn.

The most common fungicides used are: benomyl, anilazine, and thiophanate.

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 well in the morning hours, remove excess thatch, and follow a fertilization schedule to help increase the amount of nitrogen levels in your lawn.

No cure once established.


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; follow a fertilization schedule to help increase the amount of nitrogen levels in your lawn.

The most common fungicides used on Rust are: Triadimefon and Anilazine.

Grease Spot

Grease Spot 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.

The most common fungicide used on Grease Spot is metalaxyl.

Red Thread

Red Thread is most common to Fescues, Ryegrasses, and Kentucky Bluegrass 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 best prevention for Red Thread is aerate often and remove thatch. Mowing to proper levels, reduce shade on lawn, follow a regular fertilization schedule.

The most common fungicide used on Red Thread is chlorothalonil.

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 dethatch lawn.


Diagnosing lawn diseases