Managing Turfgrass Diseases
Turfgrass Diseases
| Fairy Ring, various Basidiomycetes (Mushroom fungi) |
|---|
Symptoms and signs
Fairy rings typically appear as rings of dark green and fast-growing turf. They may also appear as rings of slow-growing or killed turf. The bands of affected turf are from 4 inches to a foot in width, forming more or less continuous rings ranging from 3 to 200 feet across. In some instances, the center of a stimulated band may contain weakened or dead grass, or bands may have an inner zone of stimulated grass edged with dead or stunted turf on either side.
 |
|
Symptoms of fairy ring on home lawn. |
|---|
The first visible evidence of a new fairy ring is usually a cluster of mushrooms or toadstools. They usually appear at the outer edge of rings in late summer or early fall, during periods of high soil moisture.
 |
|
Mushrooms produced by fairy ring fungus. |
|---|
Disease cycle
Fairy rings are produced by colonies of mushroom fungi that live in soil and thatch. These colonies obtain food from decaying organic matter and grow outward radially, increasing in size year after year. The ring of stimulated grass is thought to be caused by nitrogen substances produced by the breakdown of organic matter by the fungi. The fungi usually do not attack grass, but sometimes they repel water, resulting in death of the turf due to drought. The causal fungi are spread when fungal threads, bits of mushrooms, or spores from the mushrooms are introduced into soil under a turf area.
Cultural control
Try to maintain a sufficient growth rate of the grass. Mow frequently to minimize the differences in grass vigor between the ring and the rest of the lawn. At times, large areas may be killed by fairy rings. When the grass is killed, it may be possible to remove the sod and the top 6 inches of soil and then reseed or resod. However, this practice does not always work. Sometimes nothing, not even weeds, will grow in areas killed by fairy rings.
Chemical control
Attempts to control fairy rings with fungicide drenches or soil fumigation have met with little or no success.
| Gray Snow Mold, Typhula incarnata |
|---|
Snow mold diseases occur during the winter and/or late spring under snow cover. There are several snow mold diseases that affect turfgrasses in the northeastern United States. The two most common of these are gray snow mold and pink snow mold.
 |
|
Gray snow mold on home lawn. |
|---|
Symptoms and signs
This disease is usually noticed first as the snow melts in the spring. It is commonly found in those turf areas of greatest snow accumulation, such as along driveways or over the brink of a hill where snow drifts tend to accumulate. The most notable symptoms are white crusted areas of grass in which blades are dead, bleached, and matted together. These bleached areas range from several inches to several feet across. The chief diagnostic feature of gray snow mold is the presence of hard pinhead-sized fungal bodies called sclerotia. These light to dark brown sclerotia are embedded in the leaves and crowns of the infected grass plants.
 |
|
Matted leaves of gray snow mold-affected turf. |
|---|
Disease cycle
Sclerotia oversummer in thatch, clippings, and the crown area of the grass plants. They germinate in fall and produce mycelial growth beneath the snow cover and infect plants. Gray snow mold seldom occurs except under snow cover when the soil is not frozen. In most instances, the fungus kills the blades of the plant, but does not kill the crown and roots.
 |
|
Sclerotia of Typhula incarnata, cause of gray snow mold. |
|---|
Cultural control
Gray snow mold usually can be managed successfully in home lawns without the use of fungicides. Keep the turf mowed well into the fall to avoid leaving unclipped grass that tends to fall over and mat when snow falls. Try to avoid creating long-lasting snow banks when removing and piling snow from sidewalks and driveways. When symptoms appear at snow melt in the spring, rake the infected areas and break the crusted, matted leaves to encourage new growth. Kentucky bluegrass and the fine fescues tend to be more resistant to gray snow mold than creeping bentgrass, perennial ryegrass, and tall fescue.
Chemical control
If gray snow mold tends to occur even though the cultural practices are correct, fungicides may be considered. Apply the fungicide prior to the first permanent snow cover in the fall. In many areas, this may be around Thanksgiving. A single application at this time usually will provide a satisfactory measure of control. Applying fungicides after the symptoms appear in the spring is of no value.