Ascochyta leaf blight is one of the biggest disease problems in lawns. Ascochyta is a fungus most common in Kentucky bluegrass and hybrid bluegrasses it can also be found on fescue and ryegrass.
Every year this stress induced disease shows up on the leaves of new and established turf grasses.
Ascochyta is most common when spring turns into summer and cool, wet temperatures turn hot and dry. During the outbreak there is often irregular patches of straw colored grass throughout the lawn. Leaves of the grass look bleached. This color change happens quickly, almost overnight. Though the lawn appears dead it is not.
Proper turf management is the best defense against Ascochyta leaf blight. Adjust sprinklers; insufficient irrigation adds to turf stress. Keep mower blades sharp. Adjust mower to a higher setting when mowing during the occurrence of the disease and do not mow as often. If needed, aerate in spring when roots are actively growing. Properly fertilize based on turf type and season.
Be patient. Ascochyta is like a common cold in people. It can take several weeks for this fungal disease to run its course. Fungicides are essentially ineffective while the addition of Turf Master High Phosphorus fertilizer will help with new growth.