This is a common disease list for turf grasses. It is far from a complete list, however, it is our intention to expand this area as time becomes available.
Leaf Blight (fungal – Bipolaris cynodontis, Drechslera gigantea, Bipolaris stenospila): Small, brown-to-purple lesions occur on the leaf blades. Leaf spots are usually more numerous near the collar area of the leaf blade, possibly because of accumulation in this area of spores washed from other portions of the leaf. Severely affected leaves will turn reddish-brown then wither and die. In the early stages, a severely affected turf area may have an overall purple cast. As the disease progresses, the grass gradually thins and the condition becomes advanced before a disease is suspected and verified by the presence of leaf spots. Under severe disease conditions, a sheath and crown rot may be evident and the grass killed in patches.
Smut (fungus – Ustilago cynodonis): Smut galls replace the seed in the spike. The inflorescence is often distorted. The fungus is systemic within the plant, therefore, conventional fungicides will not control the disease. Control through the prevention of seed head development by close mowing and keeping the grass in a vegetative growing condition.
Cottony Blight, Greasy Spot (fungus – Pythium aphanidermatum): Grass is rapidly killed. Affected spots may be several inches in diameter. In the early stages, affected grass appears dark and water-soaked. It will later collapse and appear to be matted together. When the disease is very active, mycelium of the pathogen grows profusely over affected plants so that diseased areas have a cotton-like appearance. The hybrid bermudas are frequently more susceptible to this disease than common bermuda grass. The disease is more prevalent during rainy, foggy weather and in low lying areas of golf courses where air circulation is poor.
Spring Dead Spot (cause unknown): When bermuda grass begins regrowth in the early spring, well-defined circular dead spots become evident. Individual spots may vary in size from a few inches to three to four feet in diameter. The margins of the affected areas are usually even, but may become irregular when individual spots coalesce to form large areas of dead grass several feet in diameter. The foliage of the dead grass assumes a bleached straw color, while the stolons and roots are characterized by a black rot. Spring Dead Spot seems to be a crown, root and stolon rot of dormant grass.
Fading Out (fungus – Curvularia sp.): Fading Out is a serious disease of bermuda grass, particularly on fairways. This condition develops more rapidly during the summer and when grass is stressed because of drought conditions and low fertility. Large dead areas will appear in the turf.
Fairy Rings (fungi – Agaricus sp., Marasmius oreades): There are many soil inhabiting fungi responsible for Fairy Ring on golf courses. Fairy Ring first appears as arcs of circles of dark green, stimulated grass surrounded by areas of light green or dead grass. There are frequently several distinct rings in the same area. Mushrooms or toadstools develop in the band of stimulated grass during rainy periods of spring and fall or following heavy irrigation. The band of green grass sometimes four to five inches wide, is due to increased nitrogen made available to the grass as the fungus breaks down organic matter in the soil. The dead grass is associated with depletion of soil water, since the soil is rendered impervious to water by the great network of fungal mycelium. Fairy Ring is quite often associated with high amounts of organic matter. Dethatching or verticutting greens and fairways will help reduce the incidence of Fairy Ring.
Nematode (nematode – many species): Symptoms often occur as areas of low fertility, even where fertilizers have been applied. This occurs when nematodes feeding on roots reduce their ability to absorb water and nutrients. Nematode damage often may be more severe on greens and tee boxes because of the higher amount of organic matter and more sandy loam type soil.
Slime Mold (fungus – Physarum sp. and Fuligo sp.): A dark gray-to-black crust-like material will form on the leaves and stems of bermudagrass. The soot-type material rubs off easily on shoes and clothing. Slime Mold derives its nourishment from decaying organic matter splashed upon the leaves and stems rather than from the grass. The slime mold does not feed on the green grass and causes no damage other than shading. It can be removed from the grass by applying water under pressure with a water hose or by brushing with a broom.
Fusarium Blight (fungus – Fusarium sp.): Diseased areas are first light green, then fade rapidly to a straw color. Such areas vary from a few inches to more than two feet in diameter and may be circular,crescent-shaped, or streaked. The patch of green grass can often be seen in the central portion of the circular area, creating a frog’s eye effect. Lesions on individual blades are irregular in outline and often extend the full width of the blade. They may extend from the cut tip toward the base. Plants are killed when crown tissues are invaded and extensive damage occurs when diseased grass areas are numerous and run together. Using a sound cultural practice that will keep the grass growing vigorously will help control Fusarium Blight.
Brown Patch (fungus – Rhizoctonia solani): This disease occurs in the late spring or early fall. It is characterized by circular patterns of dead grass blades in the turf. These range from 1-50 feet in diameter. Blades and sheather are pulled easily from stolons because of deterioration in the attachment area. Stolons often remain green. In 2-3 weeks, new leaves may emerge in the center of the circular patch giving the diseased areas a doughnut-shaped appearance. The entire spot eventually may become green during a long growing season. Disease development occurs most rapidly in temperatures between 75-85 degrees F when free moisture is present. Fungal activity stops when the air temperature reaches 90 degrees F. This explains seasonal development. Some lawns are affected almost every year, while others are damaged only occasionally. Fungicide application should be made when brown patch is expected. On lawns where brown patch occurs occasionally, apply fungicide when the disease first appears.
“Helminthosporium” Leaf Spot (fungus – Bipolaris sp., Drechslera sp.): Symptoms of this fungal disease appear as irregular patches ranging in size from two to several feet in diameter. Infections on leaves appear as small, olive green spots which enlarge to form dark blotches. Infected leaves die and fade to a light tan color. The entire plant is killed when the root rot phase of this disease develops. The disease-causing fungus overwinters in thatch at the base of the plant and acts as a pathogen when weather conditions favor its development during the growing season. Chemical fungicides are effective in control.
Dollar Spot – Small Brown Patch (fungus – Sclerotinia homeocarpa): The disease appears as round, brown or bleached spots the size of a silver dollar or slightly larger. Lesions may be seen on the edges of leaf blades. These cause death of leaf tips. During disease activity, fungal growth appearing like fine cobweb growth, may be present on leaf blades in early morning dew. This disease can occur any time during the year, but it is most prevalent in the late spring or early fall along with the hot, humid days and cool nights. Improved bermuda grass, zoysia grass and bahia- grass are more susceptible. Adequate nitrogen and spraying with a turf fungicide is recommended to control the disease.
Pythium Blight (fungus – Pythium aphanidermatum): Affects improved bermuda grass. Infected grass rapidly dies in spots or streaks. In early stages of infection, the affected spots may have a “cottony” appearance due to the abundant fungal growth. The disease occurs in poorly drained areas during warm, humid weather. Fungicides are effective for control.
Rust (fungus – Puccinia cynodontis): Plants affected with rust have a chlorotic appearance, and stands may begin to thin. Orange-colored linear pustules or raised bumps are evident on leaf blades. These vary in appearance, depending on the species involved. Pustules are difficult to see on affected St. Augustine grass unless the blades are examined with a hand lens. Zoysia grass is affected more than either St. Augustine or bermuda grass. Rust is most damaging during mild, warm weather. Rust diseases can be controlled by using fungicides.