Photos by A. H. McCain

Click on images to enlarge.

Hosts

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

Symptoms

Lawns infested with Fusarium blight have small, circular grayish to straw-colored areas of dead grass. These circular spots may range from a few inches up to a foot in diameter. Some plants in the center may survive, giving the turf a frog-eye appearance. The crown or basal area of dead stems has a reddish rot and is hard and tough. The dead foliage appears straw-colored.

Conditions favoring disease

Daytime temperatures of 85° to 95°F favor Fusarium blight. Drought-stressed areas in full sun are most likely to exhibit the disease. Fusarium blight survives in thatch and grass residues.

Prevention and management

Follow proper fertilization and irrigation requirements for your turf species. When overseeding bluegrass, use a mixture of 20% perennial ryegrass. Mow at the highest recommended height for your turf species. Dethatch if you have a thatch layer more than 1/2 inch (1.2 cm) thick. Consider replanting with other turf species that are not susceptible to Fusarium blight. Fungicides are available but do not give complete control in California. If used, make spring applications before or just after symptoms appear.

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