Lawn Care: Lawn Diseases

Lawn Diseases
Of all the pests that damage lawns, fungus diseases are one of the most difficult to tame. There are hundreds of diseases that can infect your turf. Some are relatively harmless, others can destroy an entire lawn in a very short time.

Disease travels by foot, water and air.
Fungus spores spread on the wheels of lawn mowers, on the shoes of children, on the droplets of rain that bounce from plant to plant during rain or watering, or blow like microscopic seeds across your lawn. Every lawn has disease organisms. The trick is not letting them get the upper hand.

Prevention is the best cure.
To reduce disease, keep the lawn healthy and growing with proper feeding, mowing, watering, and thatch control measures. Some grass types are much less susceptible to fungus attacks. Consider planting disease-resistant varieties when you seed.

With treatment, control is the goal.
Disease treatments do not usually eliminate the disease from the lawn. Instead, they suppress activity for a period of a few days to several weeks. The goal is to keep the disease in check long enough for the grass to recover or the weather conditions to change. Often, several treatments are needed.

Are they really a threat?
Some of the more common diseases facing residents of Western New York include; snow mold, rust, dollar spot and red thread. Most of the common diseases are weather-related. Some of them require control and some don't – most of them can be handled through good cultural practices.

Rust
Fungus
Puccinia
Symptoms
Thin, weakened turf that appears covered with an orange-red or yellow powdery dust.
Powder will discolor shoes and clothing.
Grasses susceptible
All cool season turfgrasses, especially perennial ryegrass.
Conditions favoring disease
Warm nights (68-86 degrees F/ 20-30 degrees C), wet leaves, and low light areas (shady sites or cloudy weather).
Most severe mid to late summer into fall when turf is not actively growing or under stress.
Cultural options:
Maintain adequate fertility.
Minimize leaf wetness.
Avoid drought stress (proper watering).

If you need more help or information with this topic or any other lawn or tree care questions, please contact us.

Dollar Spot
Fungus
Sclerotinia homoeocarpa
Symptoms
On closely mowed turf: Collection of silver dollar size, tannish brown to whitish spots. Turf appears speckled or mottled.
On residential turf: Collection of 1 inch to 6 inch diameter bleached white patches.
Grasses susceptible
All cool season turfgrasses.
Conditions favoring disease
Warm days (60-90 degrees F/ 16-32 degrees C) and cool nights above (50 degrees F/ 10 degrees C).
Prolonged leaf wetness, dew, and high humidity.
Dry soils with low nitrogen fertility.
Cultural options
Maintain adequate fertility.
Reduce compaction and limit thatch.
Minimize leaf wetness.
Avoid drought stress (proper watering).

If you need more help or information with this topic or any other lawn or tree care questions, please contact us.

Red Thread (or Pink Patch)
Fungus
Corticium fuciforme
Symptoms
Coral-pink to red fungus strands may be seen on leaves and leaf sheaths binding leaves together. Affected turf areas are usually more or less circular and vary from 2 to 15 inches in diameter. When dry, the pink strands resemble red threads. The infected leaf first appears water-soaked, but rapidly dies, becoming light tan. Leaves, and often the sheaths, are killed.
Grasses susceptible
Bentgrass, bermudagrass, bluegrass, fescue and ryegrass.
Conditions favoring disease
Red thread is most serious during periods of prolonged cool, wet weather, especially on turf deficient in nitrogen.
How fungus survives
The fungus survives unfavorable conditions as pinkish or red gelatinous crusts of fungus threads. When conditions are favorable, the crusts resume growth and fungus threads infect leaves.

Snow Mold
Winter weather conditions are very conducive to snow mold!

When the snow disappears from your lawn, there may be areas of weak or dead turf. Often this damage is caused by a disease known as Snow Mold.
What is snow mold?
There are two types of snow mold, Gray Snow Mold (Typhula spp) and Pink Snow Mold (Fusarium Nivale). Both types of snow mold develop under snow covers or prolonged periods of cool, wet weather. The optimum temperatures are in the 32 to 45 degree F range for both, however, the pink snow mold can cause significant damage at temperatures of 65 degrees. Both snow molds develop most rapidly when snow has fallen on unfrozen ground.
How to identify gray snow mold.
Where snow mold has been active, the turf commonly develops rough circular spots of matted, silver-gray turf. Often these spots are so numerous that an entire area may be disfigured. The trouble is most likely to be seen on the shaded side of a building, in the shade of trees and shrubs, or similar areas where moisture remains for a long time in late winter.
How to identify pink snow mold.
As pink snow mold develops, the initial infections are irregular patches of pale yellow grass, ranging from two inches to over one foot in diameter. As the disease develops further, the individual blades will take on a bleached appearance and the patches become whitish-gray. For this reason, pink snow mold is often confused with gray snow mold.
Both snow molds develop mycelium (which resemble cob-webs) that form a white mat under prolonged moist conditions. However, there is normally more mycelium with gray snow mold.
How to control snow mold
Once snow mold damage has occurred, the only possible procedure is to loosen the discolored, matted grass with a leaf rake (without digging into the soil), fertilize the entire lawn and see what will develop once good growing weather is at hand. Often the snow mold fungus kills only the tops of the plants and they recover with a few weeks of good growing weather. In more serious instances entire areas of turf, roots and all, will be destroyed and the spots will not recover. After a few weeks of good growing weather, it is reasonable to assume that any turf that has not recovered, will not do so. Then it is the time to do any necessary patching by loosening the soil and planting more seed. The delay to see what may develop is usually well worthwhile. Often the most devastating attacks of snow mold will recover without any reseeding.

See our Tree Disease page

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