Ascochyta leaf blight is a fungal disease targeting grasses like Kentucky bluegrass, Ryegrass and Texas hybrid bluegrass. Ascochyta can be a big problem in lawns after a cool, wet spring followed by hot, dry summer months. Every year this stress induced fungal disease shows up on leaves of new and established turf grasses.
During the Ascochyta outbreak there is often irregular patches of straw colored grass throughout the lawn. Up close leaves of the grass look bleached. Color change happens quickly, almost overnight. Though the lawn appears dead it is not. Ascochyta fungus is primarily a leaf fungus rarely affecting the crown or root of the plant.
Proper turf management is the best defense against Ascochyta leaf blight. Adjust sprinklers and watering times. Insufficient irrigation adds to turf stress. Water and fertilize appropriately based on sod type and season. Keep mower blades sharp. Adjust mower to a higher setting when mowing during the occurrence of the disease and do not mow as often.
Like the common cold in people it can take several weeks for Ascochyta to run its course. Fungicides are essentially ineffective. Be patient, allow lawn rest. Limit use until disease has diminished. Add extra water and nutrients. Supplementing lawn with Turf Master High Phosphorus fertilizer will help with new growth.