Summer Patch of Bluegrass
Summer patch is a common disease of bluegrass in the Kansas City area. It is extremely hard for homeowners to control this disease once it is active, but proper cultural practices will help reduce the damage from this soil borne disease.
Symptoms of summer patch develop in late June through August and often reappear in the same location year after year. The blighted turf areas form throughout the lawn often with healthy grass occurring within the center of dead grass. This characteristic is sometimes called a frog eye pattern.
Control of summer patch with fungicides is difficult due to the fact that the fungus colonizes the roots and crowns of the plants in May or early June with the symptoms not appearing for more than a month. Infected roots die and then during hot periods the dead grass appears.
Cultural practices will suppress disease development. Turf should be maintained in a vigorous, but not over fertilized condition. Avoid excessive spring and summer fertilizations. Mowing heights should be maintained above 2 ½ inches and thatch should be kept in check by core aerating yearly. Finally, avoid light frequent applications of water. Lawns should be watered deeply but infrequently about every five to seven days depending on weather and the level of maintenance.
Certain cultivars of bluegrass show some tolerance to summer patch and should be used in areas where it is a problem. Cultivars include Adelphi, Admiral, America, Baron, Bristol, Challenge, Columbia, Eclipse, Majestic and Monopoly.
Chemical applications would be required about every three to four weeks starting in mid May for control. Extension recommendations discourage heavy use of fungicides on home lawns due to expense and variability of results.
For more information refer to the following K-State link. (link name: Summer Patch