Symptoms and Signs:

Leaves infected with the Ascochyta fungus often exhibit a bleached tip dieback that extends approximately a third to halfway down the leaf blade. The margin between healthy and diseased tissue is abrupt and slightly pinched, but doesn’t have the dark brown to purple banding that is characteristic of another disease called dollar spot. In other cases leaves may exhibit white banding or entirely collapse and shrivel. These leaf symptoms resemble heat or drought stress.

The Ascochyta fungus produces minute yellow to dark brown, flask-shaped fungal fruiting bodies called pycnidia in diseased leaf tissue. These fruiting bodies, which are easier to view with the aid of a hand lens, are peppered throughout the dead leaves and can be very useful as a diagnostic feature.

Management:

Reduce thatch and promote water penetration through the soil by yearly aerification. Maintain grass height between 2 ½ and 3 inches. Minimize wounding of the leaf blades by maintaining sharp mower blades. Avoid mowing during wet weather, especially when Ascochyta blight is active. Reduce mowing frequency and increase mowing height during Ascochyta outbreaks. Although the fungus can be spread from one location to another on grass clippings it is unlikely to contribute significantly to disease development because the fungus is already present throughout every lawn. Similarly collecting clippings while mowing to reduce the amount of fungus is unlikely to reduce disease severity. The disease is more likely intensified by environmental factors and not the quantity of fungus present.

Try to maintain uniform soil moisture. Check the irrigation system to make sure all irrigation heads are working properly and that water is being distributed uniformly to avoid drought stress. On the other hand excessive irrigation and poorly drained soils may also promote disease development.

Ascochyta blight is primarily a leaf and not a root or crown disease so it rarely causes plant mortality. Turfgrass usually recovers completely after a couple of weeks. Although several fungicides will inhibit Ascochyta growth, they can be expensive and difficult to apply. Furthermore Ascochyta leaf blight development is sporadic and rapid, making timing of preventive and curative fungicide applications difficult.

Please check the "Extension Agents' Handbook of Insects, Plant Disease and Weed Control".