Fescue Has Purple Spots

Leaf Spot

• Leaf spot thrives in high humidity. Fungal spores need only a few hours to germinate and spread, according to the University of Rhode Island Landscape Horticulture Program. Spring's rainy weather can encourage a high population of fungal spores. Spores may spread across the lawn through the wind, rain or lawn mower. Summer's heat and moisture ushers in another influx of leaf spot fungal spores. Gardeners may see more damage to the yard if their grass is water stressed. Leaf spot is not as active in the fall as it is in the spring, but it can damage areas of the yard.

Damage

• Leaf spot's fungal spores penetrate grass sheaths and cause red to purplish spots with tan centers, reports the North Dakota State University Extension. These spots may coalesce which causes blighting or death to the tips of the grass blade. Leaf spot can turn into melting out disease when the spots move down to the root system of the grass. Once the fungal disease has invaded the root system, you may see large patches of grass die out.

Treatment

• Gardeners must apply a fungicide to their lawn when they notice signs of leaf spot because once the disease moves down to the roots, there is little that can be done. Apply a fungicide to the lawn every five to 10 days to treat the disease. Avoid applying fungicide when temperatures exceed 90 degrees Fahrenheit or to a water-stressed lawn. Areas that have died out must be dug up and reseeded with fescue seed.

Prevention

• Apply a slow-release fertilizer to your fescue grass in the spring. Use 1 lb. of nitrogen per 1,000 square feet, recommends Texas A&M University. Avoid using quick-release fertilizer because a flush of growth can encourage leaf spot. Sharpen your lawn mower's blades at the beginning of each growing season. Dull blades wound grass, creating a pathway for fungal diseases such as leaf spot to enter. Refrain from cutting more than one-third of your grass blade at a time because it causes a weak root system.