Photos by A. H. McCain

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Hosts

Annual bluegrass (a common weed in turf), Kentucky bluegrass

Symptoms

Anthracnose appears in the lawn as irregular patches of brown grass, 2 to 12 inches (5 - 30 cm) in diameter. Brown or tan blotches are present on the leaves. Black, spiky fruiting structures (acervuli) occur on dead grass blades and are key to identifying this disease. The older growth is affected in advance of newly developed leaves. The new growth may remain green.

Conditions favoring disease

Anthracnose is favored by warm temperatures ranging from 80° to 95°F and occurs primarily in the spring and summer. Extended periods of leaf wetness, soil fertility, high compaction, and high soil salinity contribute to disease development.

Prevention and management

Practices that limit the length of time that leaves remain wet after irrigation will reduce infection. Reduce shade by pruning trees and shrubs that block air movement or light to the grass. Improve soil aeration. Avoid drought stress and do not water at night. Fertilize using the recommended rate for your turf species. Avoid fertilizing during warm months. Increase your mowing height to reduce stress. Choose turf species other than bluegrass that are not susceptible to the disease. If the problem occurs on weedy annual bluegrass in your lawn, control the annual bluegrass. Fungicides are generally not warranted in home lawns.

For more information on lawn diseases, refer to:
Pest Notes: Lawn Diseases: Prevention and Management