Disease Control

Disease. It’s the threat you don’t see coming, and when it strikes it can lay waste to your turf, shut down your course or throw a wrench in your business operation. BASF helps turf professionals protect the health of their turf with a wide-array of broad-spectrum disease management solutions that keeps turfgrass strong and resistant to disease throughout the year.

Common Turf Diseases

Disease Name: A-L

Anthracnose

Colletotrichum graminicola

Anthracnose of turfgrass is found in many areas and climates. There are two types of anthracnose: basal and foliar. The pattern of symptoms depends largely on weather conditions. Water-soaked stem lesions become dark in color and the leaf blades eventually yellow and die. The central stem can be pulled from the plant quite easily revealing a blackened base. Reddish brown lesions may occur when warm weather, dry soil and increased humidity within the turf canopy occur. Reddish brown irregular patterns on the turf may form as the disease develops. Over time, the patterns turn yellow, tan then brown. Yellowing is stress-related. The fungus, Colletotrichum graminicola, over-winters on living plant material. Stressed turfgrass, specifically annual bluegrass, bentgrass and ryegrass, are most susceptible to infection. The fungus penetrates the root, crown, and/or leaf tissue during high humidity and wet weather conditions.

Bentgrass Dead Spot

Ophiosphaerella agrostis

Dead spot is a fairly new disease caused by a fungus, Ophiosphaerella agrostis. The disease appears to be more severe on newly established golf course greens under 4 years of age. Initial symptoms appear as small reddish spots about 1 to 2 cm in diameter. Spots gradually enlarge to a maximum of approximately 6 cm and have a characteristic tan center with a reddish brown margin. Open, exposed areas also appear to be affected more severely. The fungus invades the roots and crowns of susceptible species and affects the plant's ability to transport water. Wilting occurs as a result of severe infection, especially during the heat of the summer. Reproductive structures known as pseudothecia may be found in infected leaf tissues and in dead tissues. These structures are black, flask-shaped, and embedded in the plant tissue. They release spores that cause new infections. Symptoms are more severe in hot and dry weather, but the fungus can remain active until a hard frost.

Bermudagrass Decline

Gaeumannomyces graminis var. graminis

Bermudagrass decline is a root rot disease. Because the roots are affected, they will not be able to efficiently obtain water or nutrients from the soil, nor will they be able to store the products from photosynthesis. Symptoms observed on the leaves are the result of pathogen activity on the root system. The fungus does not attack leaves. Prolonged periods of rainfall are most conducive to this disease. Any stress placed on the turfgrass will encourage or worsen the disease. All warm-season turfgrasses can be affected. Initial symptoms of bermudagrass decline include yellow or light green chlorotic patches, 8 to 24 inches in diameter. Chlorotic leaf blades may develop next to green shoots at the margins of the diseased area. Roots will initially be thin and off-white in color with isolated black lesions. Entire plants may eventually die, resulting in irregular patches of thinning grass and, if not controlled, bare patches may develop.

Brown Patch

Rhizoctonia solani

Brown patch is a fungal disease caused by Rhizoctonia spp. This disease is favored by hot, humid and cloudy weather. Under conditions favorable to the disease, leaves can be killed in 12 to 24 hours. The disease is generally seen in summer and early autumn, although there are strains of this fungus that cause disease at other times of the year. Round or irregularly shaped patches can appear very quickly on turf that is cut closely, such as golf greens, or on turf that is very wet. At first the patches are purplish green in color, but they soon fade to light brown. If the weather is warm and humid, the fungus continues to invade new grass on the edges of the patch, so that there may be a dark purplish to grayish brown border or ring surrounding the spots. This is usually noticeable only in the early morning while the grass is still moist from dew. Dense stands of well-fertilized turf are generally most susceptible to this disease.

Dollar Spot

Sclerotinia homoeocarpa

The disease name of dollar spot is derived from the dead straw-colored spots about the size of a silver dollar. It occurs on bluegrasses, bentgrasses, fescues, zoysia, and seashore paspalum. Under close mowing conditions the circular straw-colored spots are distinctly outlined; however, with higher cutting heights, the bleached turf spots are irregularly shaped. In the early morning, when dew is still on the grass, a white web-like growth of the fungus may be seen over the spot. If the spots coalesce, a more general blight may be observed. On individual grass blades the damaged tissues are first watersoaked and dark colored. As they dry, the lesions turn light tan to straw-colored with a reddish brown border. Dollar spot is most common in early summer, late summer and early fall in humid weather with warm days and cool nights. Dollar spot is less prominent in very hot weather.

Fairy Ring

Basidiomycete fungi

During the spring or summer a circle or arc of stimulated grass or toadstools may appear in lawns. These are turf abnormalities called fairy rings. The rings can be up to 20 meters in diameter, but most are between 1/2 meter and 5 meters across. A fungus that plagues many courses and lawns, fairy ring is caused by mushroom fungi that live in the soil and thatch layer. Early symptoms include circular rings of overly green grass. The fungus has three types: Type I rings include a center section of dead grass surrounded by a ring of dark green grass; Type II rings do not have dead grass - only a band of dark green turf, sometimes with mushrooms; Type III rings have only a ring of mushrooms without affecting the grass color. Fairy rings usually do not present a lethal threat to a lawn or other turf, but sometimes a ring of dead grass occurs in addition to the ring of stimulated grass growth. Fairy rings normally recur each year, and their diameter slowly increases.

Fusarium Patch

Microdochium nivale

Fusarium patch is a fungal disease that attacks lawns. Infection occurs most often at temperatures between 32° and 50°F, conditions which are present under snow, therefore giving it the common name of snow mold. However, snow cover is not required under conditions of extended leaf wetness. Severe outbreaks can occur at 65°F anytime of the year in some regions. Symptoms appear later as irregular patches of yellow then brown grass up to 30 cm in diameter when there is high humidity and temperatures of up to 65°F. This usually occurs between May and September. When damp conditions prevail, the dead blades of grass become slimy and are covered in a light pink bloom.

Gray Leaf Spot

Pyricularia grisea

Gray leaf spot, caused by the fungus Pyricularia grisea, is a disease that affects mainly annual and perennial ryegrasses and tall fescue; St. Augustinegrass and kikuyugrass are also susceptible. Areas with extended leaf wetness and high nitrogen concentration are more susceptible to severe outbreak and infection. Although it is common in the southern states, infections have been found as far north as Long Island, the lower Hudson Valley of New York State, and Pennsylvania. Infections and diseased tissue can appear quite quickly. Damage is usually noticed during the warmer months of late summer. If weather conditions are hot, humid and dry for extended periods, the damaged spots may grow up to 40 cm in diameter. The disease progresses so quickly that large areas of turf can be lost within a few days. The pathogen can produce large amounts of infectious spores in a very short period of time causing symptomatic tissue to become evident and decline very quickly. Spores land on a susceptible host and germinate within a few hours. The pathogen then invades the leaf tissue through the cut leaf tips. Symptoms can appear within hours of infection. Infected leaves may have water-soaked lesions and appear chlorotic. The youngest leaves often take on a characteristic fishhook shape. The disease is most severe on young seedlings. Damaged spots of turf first appear reddish-brown in color and 2 to 5 cm in diameter. A yellow margin may surround the damaged spot and the leaf blades may have dark brown borders.

Gray Snow Mold

Typhula incarnata, T. ishikariensis

Gray snow mold is caused by Typhula incarnata and related species. It is a true snow mold and appears as roughly circular bleached patches up to 60 cm in diameter. Severe outbreaks develop in areas of prolonged, persistent snow cover. Soon after the snow melts, the infected grass may be matted and surrounded by a white to gray halo of fluffy fungal growth. Tiny tan or brown pea-like structures are on or imbedded in infected leaves. The severity of the disease will vary. It is particularly severe when turf has been subjected to prolonged, deep, compacted snow cover. Bentgrass is most susceptible. Although the disease is unsightly, it rarely kills the grass. This fungus produces sclerotia to help it survive the summer months and in late fall; when conditions are favorable, these sclerotia may produce mycelium that produce spores. Mycelium from the spores or sclerotia grow out and infect new plants under cover of deep snow during the winter. Where gray snow mold has occurred once, it is likely to recur if left unmanaged.

Helminthosporium Leaf Spot

Bipolaris spp.

Helminthosporium leaf spot is caused by several fungi in the genus Bipolaris. The pathogens are favored by cool to moderate temperatures (60° to 70°F) during wet or humid weather. The pathogen is likely spread by splashing rain, irrigation water, and wind. It affects mainly Kentucky bluegrass, bentgrass, ryegrass, tall fescue and creeping red fescue. Lesions may be in the form of small brown flecks, linear streaks, or oval or irregularly shaped spots. The number and size of lesions may increase, coalesce and form long streaks. Lesions are initially dark brown but become tan or gray-brown with a faint dark brown border. During wet weather, lesions develop a dense gray-brown appearance. Black conidial and mycelial growth may be apparent on individual grains in the head. Warm wet weather is ideal for development. It is most common when temperatures are ranging from 80° to 90°F and there are extended periods of rain.

Leaf Spot

Bipolaris, Drechslera, Exserohilum spp.

Leaf spots on turfgrass leaf blades begin as small red to purplish ovals that later develop tan centers of dead tissue with darker borders. The fungi that cause leaf spots directly penetrate leaf sheaths and blades at random or enter through mowing wounds. After recent nitrogen fertilization, when there is abundant moisture on the leaf blades, numerous leaf spot infections per blade can occur. The leaf spots may then coalesce and cause extensive blighting. The fungus may even invade the crowns and roots, leaving the plants weakened and rotted. This severe stage is called "melting out." Large areas of dead or badly weakened turfgrass may result. Leaf spot fungi may be active at a variety of temperatures. All are associated with frequent moisture on the leaf blades and high relative humidity.

Disease Name: M-Z

Melting Out

Drechslera poae

Typically found on bluegrass, melting out causes circular to elongated purplish or brown spots with straw-colored centers on leaf blades, leaf sheaths, and stems; symptoms first appear on shaded plants. The leaf spots may be widespread throughout the lawn, indicating spread by windborne spores. Crowns and roots are frequently affected with a dark brown rot. The crown-infected plants are weakened and may die in hot, windy weather, resulting in a thinning out of the turf in scattered areas. The fungus survives on infected bluegrass plants or grass debris and may be seedborne. Melting out thrives in cool (50 to 75° F), moist conditions. It is most severe on closely mowed turf and on turf with high nitrogen fertilization.

Pink Patch

Limonomyces roseipellis

Pink patch, formerly thought to be a form of red thread and caused by the fungus Limonomyces roseipellis, is a minor disease of frequently mowed grass. Pink patch is much more severe on either unmowed or infrequently mowed grasses that are grown under low nitrogen fertilization than it is on highly maintained turfgrasses. Although patches generally remain green, diseased turf may have a tannish cast. Affected areas in above-ground portions of coarse-textured turfgrass are irregularly shaped blotches, but distinct pinkish patches, two to six inches across, occur in creeping bentgrass. The disease occurs primarily in spring and autumn during prolonged periods of heavy dews, light rains and fog, although it may occur during the summer months between 60° and 70°F. Small, irregularly shaped areas of turf become covered with a pink to reddish film of mycelium that tends to form first along the leaf margins. Later, the entire width of the leaf blade is covered. Only leaves and sheaths are infected, and diseased leaves die from the tip downward.

Pink Snow Mold

Microdochium nivale

The fungus that causes pink snow mold produces roughly circular bleached patches up to 60 cm in diameter. Often, the mycelium of the fungus is readily visible. In contrast to gray snow mold, however, a pinkish cast to the symptomatic area might be observed under wet conditions. This disease can become severe when turf is subjected to prolonged periods of cool, wet weather from early autumn to late spring, and does not require snow cover to develop. The fungus Microdochium nivale survives unfavorable periods as dormant mycelium in infected plants and plant debris. As conditions improve for fungal growth, the fungus may begin to infect plants with little symptom development. Wet weather conditions with temperatures around 60° F will promote rapid spread of the disease. Dry, warm weather causes the fungus to revert to its dormant state. The fungus can be transmitted throughout the year on equipment, people, animals, wind or water.

Powdery Mildew

Blumeria graminis

Powdery mildews are common on many kinds of plants. Although they may look the same, each kind of plant is infected by a different species of powdery mildew fungus. Powdery mildew fungi on grasses will not infect lilacs, phlox, roses or other garden plants. Powdery mildew may appear quite suddenly, usually in shaded areas, and most commonly on Kentucky bluegrass. The grass blades may look as if they were dusted with flour. The white to gray powder is a combination of the mycelium and spores of the powdery mildew fungus. The mycelium grows over the surface of the leaf, absorbing nutrients from the plant. Later, the leaf may turn yellowish and begin to dry up and die, but the leaves often support the presence of the powdery mildew fungus for some time without significant injury. Powdery mildew is most common in turf from July to September, and occasionally in the spring. It occurs mainly during overcast periods of cool, moist weather. Spores can infect leaves in less than two hours, and new spores can be produced in abundance in less than a week. Air currents carry the spores to new grass plants. Disease development can be so rapid that powdery mildew may seem to appear very suddenly.

Pythium Blight

Pythium aphanidermatum

This disease begins in mature lawns as small slimy or greasy looking spots. The spots may assume a reddish color if weather conditions become cooler and drier. When the turfgrass is wet or where air circulation is poor, the cottony, white, web-like mycelium of the fungus may be observed. This disease can develop rapidly and extensively in poorly drained areas and is especially prone to following surface drainage channels. Pythium fungi are "water molds," which produce microscopic swimming spores. These spores are attracted to living plants. Plants that have undergone recent nitrogen fertilization are more susceptible to infection. The fungi grow well in soil and thatch in wet weather and survive as thick-walled resting spores during adverse conditions. Pythium species are present in every soil and will grow rapidly under conducive conditions. The disease occurs most commonly in perennial ryegrass lawns.

Rapid Blight

Labyrinthula terrestris

Rapid blight is a new disease of cool-season turfgrass. Early symptoms of this disease include patches of turf that appear water-soaked, slightly sunken and darker than healthy turf. Affected turf yellows and dies. Small patches several inches across may enlarge rapidly to over a foot in diameter, coalesce and result in larger areas of dead turf. Mowing and foot traffic can increase disease incidence rapidly. In a few cases, entire plantings of cool-season turf seedlings have been lost. The disease has been consistently associated with sites with poor-quality irrigation water: high salinity and sodicity and high bicarbonate concentrations.

Red Thread

Laetisaria fuciformis

Red thread is caused by the fungus Laetisaria fuciformis. Fine-leaved fescues and perennial ryegrasses are very susceptible. Although red thread rarely kills turfgrass plants outright, it does weaken them and contributes to their decline and death from subsequent stress diseases. Red thread is favored by slow-growing, nitrogen-deficient turfgrass, excess thatch, low calcium levels in the soil, water stress, a sudden drop in temperature and misused herbicides. The fungus forms conspicuous, coral pink, orange or red mycelial masses on the grass blades and leaf sheaths. In moisture-saturated air, the gelatinous masses may completely cover the leaves and mat the blades and leaf sheaths together. Where infection is severe, diseased turf is bleached tan or yellowed in roughly circular- to irregular-shaped patches, varying from an inch to more than 1 foot in diameter. Spreading occurs by splashing or flowing water and by wind, shoes, mowers, and other turfgrass equipment. Infection and disease development are favored by air temperatures of 60 to 75° F coupled with prolonged periods of overcast weather, light rains, heavy dews, fog, and moisture-saturated air.

Rust

Puccinia, Uromyces spp.

All turfgrass species are susceptible to rust diseases. Environmental stresses contribute to the severity of the disease. When plants become diseased by the rust fungi, they are more likely to be attacked by other pathogens. When a plant is diseased, light yellow flecks on the leaves or stems become long, yellow stripes parallel to the veins. These will split open and spores will dust out. The spores range in color from orange to brick-red, although they can be yellow to brown or black for some rust species. When the infection is severe, the entire area may appear the color of the spores. The turf may die in patches from the infection or the stand may be thinned and weakened. Death of the turf is possible during severe infections. This disease is favored by low light, wet leaves, and temperatures around 70° F.

Summer Patch

Magnaporthe poae

Caused by the fungus Magnaporthe poae, summer patch occurs between the hottest periods of June through September. The disease begins as scattered small round patches of thin, wilted or slow-growing turf. Initially, affected patches may be only 3 to 8 cm in diameter, but they may enlarge to about 30 cm in diameter and range from grayish green to light tan or straw-colored. As patches enlarge, they may coalesce and form crescents of yellow or tan turf. Summer patch blighted areas often occur on lawn sites that receive direct sun and are on south-facing slopes or near sidewalks, driveways, buildings, or otherwise stressed areas. In the cool weather of autumn, the grass may begin to grow into these dead areas again. The disease, however, is likely to reappear in previously affected areas the following summer, and to increase in intensity. Summer patch is less of a problem during cool summers with adequate rainfall.

Take-All Patch

Gaeumannomyces graminis var. avenae

Take-all patch is a disease caused by the fungus Gaeumannomyces graminis. Newly seeded sites tend to be most vulnerable to this fungus, especially where bentgrass is being established on soil with a high pH. Cool-season turfgrasses, such as bentgrass, are highly susceptible. Symptoms of take-all patch are most likely to appear in late spring as small, sunken, water-soaked patches of turfgrass. Where turfgrass is stressed, the affected grass may initially appear reddish brown before dying and turning a dull brown color. The roots and crown of infected plants become dark brown to black. Small circular areas of dull brown grass continue to expand throughout the growing season, spreading in size up to about 1 meter in diameter. Symptoms begin to show up as the weather becomes warmer and drier.

Yellow Patch

Rhizoctonia cerealis

Primarily a problem of bentgrass and annual bluegrass but is commonly seen in the winter on overseeded bermudagrass greens, inperennial ryegrass or rough bluegrass. Also occurs on ryegrass, tall fescues, zoysiagrass and bermudagrass. When it occurs on warm-season grasses this disease will infect in the fall as the grasses approach dormancy. Rhizoctonia cerealis remains dormant during summer and begins disease-causing activities during cool, wet weather (fall, spring, or winter) at temperatures of about 40° F. On putting greens, this disease becomes visible when tan, brown, or yellow rings appear, ranging in size from several inches to feet. On bentgrass greens, lesions are similar to brown patch that occurs in the warmer months of the year. In zoysiagrass leaf lesions, tan centers and brown borders more closely resemble dollar spot as patches. Preventative applications are needed before rings appear to control symptoms.