Disease Control (Lawns)

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. 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. And, just when you thought you had all of your lawn care problems solved. Fear not, we have some tips to help you identify and treat your lawn problems.

A disease is an abnormal condition resulting from changes in the plant's normal growth or functional processes that usually occur when 3 factors happen at the same time. A susceptible turf grass (many varieties are susceptible to certain pathogens, where others are resistant to the very same pathogen), a pathogen that can invade the turf grass, and environmental conditions that favor the growth of the pathogen.

Pathogens that can cause turf grass disease mostly fall into the fungi category, although there are several bacterial pathogens that have been discovered recently. Fungi are mostly types of parasitic plants that must gain nourishment from hosts (your turf grass). These can be further divided into types of fungi that kill their host and move on, and those fungi that require the plant to remain alive for their continued existence.

Controlling Diseases

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.

Remember, it takes 3 different factors for a disease to become a problem. Controlling any one of those 3 can cause the disease to stop. In some cases, replacing the existing turf grass variety with another variety resistance to the specific pathogen may be the answer. Although you can't control the weather, it is possible to modify your particular microclimate by increase air circulation, improving drainage, increasing the amount of sunlight reaching the turf grass, or considering a different type of ground-cover instead of turf grass.


The best treatment is prevention. Avoid circumstances that are more likely to allow diseases to infect lawns. Proper watering, mowing regularly and at the correct height (don't mow too short). In some instances, disease is spread by mowers that have recently cut infected lawns. If you hire an outside maintenance service, discuss with them precautions they take to avoid disease spread.

Thatch is also a breeding ground for many diseases. Aerate often if necessary (2 times a year) to reduce thatch to less than 1/2". Improve drainage if water regularly stands after a heavy rain. Be careful of over-watering, or watering at the wrong time of day (see watering info).

Ask a professional lawn care provider for specific treatments recommended for your specific geographic area.(See Selecting a Lawn Pro in your area)


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

Here then are a list of common lawn diseases and what can be done to prevent future infections.


Source: http://www.american-lawns.com/problems/diseases.html

First appears as small, circular, grayish green areas, ranging from a few inches up to a foot in diameter. Some plants in the center of the circles may survive, giving them a frog eye or donut appearance. The crown or basal area of the dead stems is affected with a reddish rot and is hard and tough. At times, a pink layer of the fungus can be seen near the soil line.

Light green patches that spread, turn reddish brown and then die. Caused by a soil borne fungus, often in combination with other pathogenic fungi. Primarily attacks Kentucky bluegrass.

Usually occurs in hot, dry weather. Begins as a small spot, then grows until it kills the grass.






Usually occurs with prolonged moist conditions when plants are under stress. Has irregular patches of yellow bronze, chlorotic, or blighted turfgrass.


Avoid excessively wet conditions. Use only moderate fertilization.

Snow Mold


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.

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.

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.


Watering the lawn at the correct intervals is one of the keys to preventing dollar spot as it will help the soil retain moisture. Remember it is best to water thoroughly at intermediate intervals rather than watering sparingly at short intervals



Rust gets its name from the orange, "rusty"appearance it gives leaf blades. Most commonly effecting rye grasses 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.

Red Thread


Red Thread is most common to Fescue's, Rye grasses, 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 best prevention for Red Thread is aerate often and remove thatch. Mowing to proper levels, reduce shade on lawn, follow a regular fertilization schedule. Including potassium in the fertilization program may help mildly cases.

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.

Also known as grease spot, spot blight, cottony blight.


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


Leaf Spot-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. Usually affects cool-season grasses.


Do not introduce additional nitrogen when fertilizing, aerate and detach lawn. Apply a contact fungicide when leaf spot is first noticed. Make at least 3 more applications, 7-10 days apart.

Summer Patch


Very similar to Fusarium Blight. Infection usually occurs in compacted soils, in late spring. Symptoms then appear in hot summer months.


Systemic fungicide to infected areas.




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