Disease development is dependent on susceptible plants, a favorable environment, and a pathogen. Diseases will not occur unless all factors are present simultaneously over a certain period. Management practices that favor a healthy turf such as planting improved, adapted cultivars, proper fertilization, and timely watering (for example, avoiding late evening watering) can prevent or limit turf injury by diseases.
Inspect your lawn frequently to detect diseases early. Correct identification of a disease may require the assistance of a qualified individual. Environmental stresses, improper lawn care practices, and insect pests often display symptoms that resemble diseases. If a fungicide is necessary, correctly identify the disease, select the proper fungicide, follow label directions, and apply it at the correct rate and time. Contact your county Extension agent, another qualified individual, or refer to theN.C. Agricultural Chemicals Manual for additional information.
Table 1A. Diseases of Warm-Season Grasses - Symptoms
Disease Turf affected Symptoms
Brown patch Bermudagrass Circular brown areas up to 20 ft in Rhizoctonia St. Augustine- diameter that develop during cool, spp. grass wet weather in the spring or fall. Leaves wilt and die, resulting in large brownish-tan areas. Brown patch usually is present in bermuda- grass at time of spring greenup.
Centipede decline Centipedegrass Circular dead areas appear in the spring and continue to enlarge dur- ing the summer. Grass at edge of areas may yellow, wilt, and die during stress periods.
Dollar spot Centipedegrass Straw-colored patches 2 to 6 inches Sclerotinia Bermudagrass in diameter develop in late summer. homoeocarpa Zoysiagrass Light tan lesions with reddish-brown margins develop across leaves.
Fairy rings All types Large arcs or rings of very green Mushroom-type grass, dead grass, mushrooms, puff- fungi balls, or a combination of these symptoms.
Gray leaf spot St. Augustine- Oval or circular tan lesions that Pyricularia grass are bordered by purple to brown mar- grisea gins develop in warm, wet weather. Leaves wither and die if many lesions develop, giving the turf a brownish color.
Leaf spot Bermudagrass Dark, circular, or oval-shaped Helminthosporium lesions develop on blades and stems. spp. Some lesions become red, purple, or tan with dark margins. Turf appears yellow to brown if the disease is severe and becomes thin.
Rust Zoysiagrass Small yellow specks on leaves and Puccinia stems that develop into orange or spp. red pustules. Heavily infected lawns take on orange or reddish hue and the turf becomes thin and weak. Rust is most often a problem in lawns with too much shade.
Slime mold All grasses White, gray, powdery fruiting bodies Mucilago, Fuligo that cover leaves in patches 6 to Physarum 12 inches in diameter during warm, wet weather. Fungus usually disappears during dry weather.
Spring dead spot Bermudagrass Dead spots appear in the spring as grass resumes growth, usually after lawn is at least 3 to 5 years old. Spots expand for 3 to 4 years, often developing into rings, and then disappear. Infected areas recover slowly and weeds frequently invade these areas during the summer.
Nematodes (sting) All grasses Turf becomes thin and does not grow well following fertilization and irrigation. This occurs most often in sandy soils. Roots are shallow and may be killed. Have soil samples assayed by the N.C. Department of Agriculture to determine if nematodes are a problem.
Table 1B. Diseases of Warm-Season Grasses - Time of Occurrence and Management
Disease Turf affected Management Occurs
Brown patch Bermudagrass Provide good drainage and April-June Rhizoctonia avoid excessive nitrogen spp. fertilization. The turf usually recovers in warm, dry weather.
Centipede decline Centipedegrass Maintain soil pH between April-Sept. 5 and 5.5 and avoid exces- sive rates of nitrogen (use 1 lb N or less/1,000 sq ft/yr) and phosphorus fertilizers. Maintain the turf at 1-inch mowing height and apply iron to foliage if yellow. Avoid drought stress. If nematodes are causing the decline, irrigate as needed or select another type of grass.
Dollar spot Centipedegrass Adequate fertilizer will May-Sept. Sclerotinia Bermudagrass help the turf overcome this homoeocarpa Zoysiagrass disease. Irrigate turf as needed to avoid drought stress.
Fairy rings All types Remove organic matter Jan.-Dec. Mushroom-type (stumps, waste lumber) from fungi soil before planting. Power rake to remove thatch when it exceeds 1/2 inch. Remove soil cores, spike or force water into affected areas to allow nutrient and water penetra- tion. Avoid overfertilization in an attempt to mask the green rings. Soil fumigation or rototilling and replanting may eliminate fairy rings.
Gray leaf spot St. Augustine- Avoid excessive fertiliza- Apr.-Oct. Pyricularia grass tion with nitrogen when grisea warm, humid weather is expected. Avoid late after- noon and evening watering. Prune trees and undergrowth to improve air movement and light intensity.
Leaf spot Bermudagrass Fertilize properly and May-Sept. Helminthosporium avoid close mowing in late spp. spring and summer. Keep mower blades sharp. Water deeply but infrequently and avoid prolonged leaf wetness.
Rust Zoysiagrass Ensure adequate fertiliza- May-Oct. Puccinia tion and dispose of clippings spp. when symptoms are evident. Remove excess shade and main- tain good soil moisture. Several fungicides can be used to help control this disease.
Slime mold All grasses Remove by brushing, mowing, May-Nov. Mucilago, or washing the turf. Slime Physarum, Fuligo molds are not considered spp. harmful and do not require fungicide treatment.
Spring dead spot Bermudagrass Avoid excessive nitrogen Apr.-July fertilization and do not apply nitrogen after late August. Raise mowing height and ensure adequate potassium in the fall. Reduce thatch by aerifying and pulverizing soil cores. Some fungicides can be used in the fall to control this disease.
Nematodes (sting) All grasses Plant the best-adapted turf- June-Sept. grasses and ensure adequate fertilization and irrigation to help overcome nematode damage. Nematicides are not labelled for use on residen- tial turf.
So what do you do? Use a pesticide? Or make changes in cultural practices? Both methods, and some others as well, may be needed. The balanced use of all available methods is called integrated pest management (IPM).
The idea is simple. It encourages the use of all available prevention and control methods to keep pests from reaching damaging levels. The goal is to procure good turf and minimize the influence of pesticides on man, the environment, and turf.
IPM Methods include:
When chemical control is necessary, select the proper pesticide, follow label directions, and apply when the pest is most susceptible. Treat only those areas in need. Regard pesticides as only one of many tools available in lawn care.
To learn more about integrated pest management, pest identification, lawn care, and proper use of pesticides, contact your county Cooperative Extension Center.