Lawn Diseases- Part 2

Lawn diseases can damage your lawn. Here is a continuation of lawn diseases started in "Lawn Diseases- Part 1".

Leaf Spots

Indicated by purplish black, dark reddish brown, chocolate brown,light gray, or tan spots on leaves and stems. The spots can be round or oblong and may cause entire colonies of grass to turn yellow. Turf becomes thin, weak, or dying out in round to irregular spots that enlarge during summer months. Most affected grasses are Delta, Kenblue, and Park Kentucky bluegrass.

Cultural control: Reduce the amount of shade. Improve aeration for better water drainage. Mow at top limit of cutting height.


These occur in lawns that are low I nutrients and fertility with poor drainage, high acidity, too much shade, improper watering, or a combination of these. They appear as light green to dark, fuzzy, or slimy growths that cover soil, grass, or objects such as rocks and garden ornaments. Most affected grasses are all grasses where the above mentioned conditions predominate.

Cultural control: Aerate well, rake affected area, remove causes of excess shade, use fertilizer such as ammonium sulfate.

Powdery Mildew

This mildew grows when nights are cool and days are warm. They occur mostly on bluegrasses and fescues. The mildew color is white, gray-white, and brown. Patches can be seen on leaves in shaded or poorly drained areas. The leaves can possibly yellow and wither. This is most serious on new plantings. Most affected grasses are Bermuda grass, Kentucky bluegrass, and zoysia grass.

Red Thread

This disease is sometimes called Pink Patch. It affects mostly fescues, bent, and bluegrasses. Irregularly shaped pink patches of dead grass 2 to 6 inches or more in diameter develop during cool, damp weather in spring, fall, and winter. Usually only leaves are affected. If the disease is very sever, patches turn brown and die. Characteristic: coral-pink threads bind leaves together. Most affected grasses: kentucky bluegrass, red fescue, and ryegrass.

Cultural control: Use more nitrogen


This problem is indicated by orange, reddish-brown, yellow, or black powdery deposits on leaves and leaf sheaths. If severe, leaves may yellow, wither, and die. Grass may be thinned, weakened, and more susceptible to drought, winter injury, and other diseases. Most affected grasses are Kentucky bluegrass and rye grass. All commonly grown grasses are susceptible.

Stripe smut

Long or short stripes in leaves that rupture and release dark brown or black powdery masses. Sometimes leaves are shredded, wilted, and withered. Grass can yellow and later die in patches 2 to 8 inches in diameter. Most affected grasses are bent grass and Kentucky bluegrass.

Cultural control: Do not overwater. Aerate regularly and keep thatch to a minimum.

Slime Mold

This appears in warm weather following heavy watering or rains. Small white, gray, or yellow slimy masses that grow up and over grass surfaces in round to irregular patches, shading or discoloring otherwise healthy turf. Masses dry to form bluish, gray, yellow, black, or white powdery white growths. Most affected grasses are common Kentucky bluegrass, zoysia grass, bent grass, and fescue.

Cultural control: Aerate profusely. Dethatch even if thatch layer is less than one-third inch. Cut grass to lowest limit of height for your recommended variety. has helpful information on many garden topics.

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