Disease Management in Turfgrasses
Authors: Prabhat Kumar, Namita, Ritu Jain and Sapna Panwar
Division of Floriculture and Landscaping
Indian Agricultural Research Institute, New Delhi-12

A disease is an abnormal condition affecting the body of an organism. Both living and non-living factors can cause diseases. Disease is often understood to be a condition associated with specific symptoms and signs. The visible expression of a disease on the host is known as a symptom. A sign of a disease is some type of visual expression of the pathogen. The living organism that cause plant diseases include bacteria, fungi, viruses, phytoplasmas, parasitic plants, nematodes, and other organisms capable of altering the physiology of the plant. The discoloured areas (lesion) that appear on grasses affected by leaf spot would be a symptom of that disease. Every turf manager should be familiar to the symptoms and signs of the common turf diseases. An important part of disease control is to manage the turfs in such a way that the plants remain healthy and discourage disease development.

Common diseases of turfgrasses

Leaf spot:(Bipolaris sorokiniana)

Symptoms
• Formation of lesions on the infected blades.
• Lesions begin as elongated spots with tan centers and a purple to black border.
• As the disease progresses, entire leaves and sheath may become blighted.
• Generally develop in spring and fall, but may be observed any time throughout the growing season.


Control

• Mowing the lawn at the proper height
• Removal of excess thatch layers
• Irrigate at regular interval to avoid any stress
• Avoid excess nitrogen fertilization
• Grow resistant cultivars
• Spray of mancozeb or chlorothalonil or Iprodione or liquid copper concentrate fungicide.

Fairy Ring (Basidiomycetes)

Symptoms
• Circular patterns of dark green grass that sometime appears in lawn or grounds
• They may be green rings or they may have mushrooms around their perimeters particularly in the early morning hours
• The grass ring is caused by nitrogen which is released when organic matter is broken down by the fungi
• Dead ring is caused by competition of fungal hyphae with the grass.

Control

• Sufficient nitrogen application
• Sufficient water to prevent from drought
• Avoid burrying grade stakes and other wood debris
• Spray Triademefon, Azoxystrobin, Flutolanil

Brown Patch (Rhizoctonia solani)

Symptoms

• Blights the leaf blade from the tip to down
• May damage sheaths and crowns as it progress
• Gray to black mycelium often forms a halo around the outer edge of the infested area during the night and persists into the early morning hours
• Can attack most of the cool and warm season grasses

Control

• Include a moderate nitrogen program, particularly during spring and early summer for cool-season grass
• Remove excessive thatch
• Use of fungicides viz., mancozeb, thiram, Flutolanil, Chlorothalonil, Triademefon, Propiconazole and Triconazole

Dollar Spot (Sclerotinia homeocarpa)

Symptoms

• Silver dollar sized blighted areas appear on close mown creeping bent grass
• Blighted areas may expand to several feet wide.
• Individual blades have an ‘ hour glass’ shaped lesion that girdles the middle of the leaf blade
• The lesion is tan in the middle with a brown halo above and below
• The leaf tip may remain green and entire leaf may be blighted as the disease progresses.
• Cottony mycelia may appear on the leaves early in the morning.
• Prevalent on nitrogen deficient grasses

Control

• Proper nitrogen fertilization
• Practices to reduce thatch
• Proper irrigation
• Spray of mancozeb or chlorothalonil or liquid copper concentrate fungicide is effective against dollar spot.

Precautions for fungicides usage

• The rate of application should be the minimum, necessary to provide effective insect control.
• Liquid concentrates of some fungicides may penetrate the skin, therefore, rubber gloves should be worn and splashes washed off immediately.
• Containers of fungicides must be kept tightly closed and stored in a safe, dry place away from children, livestock, food, feeding stuffs and water supplies.
• Care should be taken not to eat or inhale any of the fungicide, while working with concentrates, so that eating or smoking should be avoided.
• Used containers should be burned or buried, or thoroughly washed before disposal.
• Unused diluted wash and washings from equipment in used containers should never be emptied into ponds, streams, rivers, etc.


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