Attack of the Blight

Attack of the Blight: How to Save Your Lawn from Ascochyta

If you’ve ever stepped outside to find large, straw-colored patches suddenly appearing in your once-green lawn, you might be dealing with Ascochyta leaf blight. This fungal disease is a common issue for Kentucky bluegrass lawns in Colorado, though it can also affect tall fescue and perennial ryegrass. While it may look alarming, the good news is that it rarely causes permanent damage.

What Causes Ascochyta Leaf Blight?

The environmental conditions that trigger Ascochyta leaf blight are not fully understood, but the disease tends to appear after cool, rainy periods followed by sudden heat and drought stress. The fungus survives in dead leaves and clippings, producing spores that spread through rain, irrigation, and mowing.

Symptoms to Watch For:

• Rapid browning of large turf areas, often overnight.
• Bleached leaf tips that extend partway down the blade.
• White banding or shriveled leaves that resemble drought stress.
• Healthy blades interspersed within affected patches.

Unlike some other turf diseases, Ascochyta does not kill the roots or crowns of the grass, meaning recovery is possible with proper lawn care.

How to Manage and Prevent Ascochyta Leaf Blight

Since fungicides are generally ineffective due to the disease’s sudden onset and quick recovery, the best approach is good turf management. Here are some key practices:

• Avoid overwatering—fluctuating soil moisture can worsen the disease.
• Mow with sharp blades and avoid cutting grass too short.
• Do not mow wet grass, as this can spread fungal spores.
• Maintain balanced fertilization to support healthy turf growth.

With proper care, affected lawns typically recover within a few weeks. If you’re dealing with persistent issues, Colorado State University Extension offers additional resources on lawn care and disease management.

For more details, check out the full CSU Extension fact sheet on Ascochyta Leaf Blight. Keep your lawn healthy, and don’t let this sneaky fungus take over your turf!