Summer Lawn Diseases: Ascochyta Leaf Blight

Ascochyta leaf blight is primarily a disease of Kentucky Bluegrass lawns. It appears as large, irregular shaped, straw colored patches.

In the summer, this disease may infect Turf Type Tall Fescue and Ryegrass lawns, as well.

The disease attacks mainly plant leaves and typically does not kill the turf. Like other diseases, activity is triggered by specific environmental conditions in the spring and summer.

While this disease may appear almost anytime during the growing season, it is most common during hot, drought conditions after a period of cool, wet days.

When identifying the disease, look for a bleached-out tip, slowly dying back toward the crown or base  of the plant. As the disease progresses, large browned out patches may appear to be dead.

Best management practices offer the most hope for control. This includes mowing at three inches with a sharp mower blade and watering three times per week for a total of at least three inches per week.

Note: In Denver, where humidity is typically low, watering as the sun sets is acceptable. Avoid mid-day watering.*

*For more details, refer to Colorado State University Extension Fact Sheet No. 2.901

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