Ascochyta Leaf Blight of Lawns

During early June we received several photos of dying lawns while neighboring lawns looked healthy and green.

Ascochyta leaf blight is the disease causing these problems. It causes large irregular patches of turf to quickly turn straw-brown in color and appear dead. From a distance the symptoms resemble drought stress. Ascochyta symptoms can appear as quickly as overnight. Infected leaves present a bleached tip dieback and the margin between healthy and disease shows a slightly pinched appearance. Some leaves may have uniform lesions affecting the entire leaf blade.

Ascochyta blight occurs on drought-stressed turf and also during periods of hot weather preceded by wet conditions. Manage the disease by reducing thatch by annual core aeration to allow better water penetration. Maintain grass height at 2.5 and 3 inches and reduce mowing frequency. Turf may look dead from a distance, but the blight does not affect bluegrass crowns and roots, so grass will recover in a matter of weeks depending on weather conditions.

Several lawns where the disease was observed have already shown quick recovery aided by the recent rainfalls that followed the weather events that incited the disease.