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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