In Iowa, we frequently see summer patch in home lawn situations where sod has been laid on heavy clay soil within the last few years. Many times, these sites occur in newer housing developments in which little topsoil has been allowed to remain. These sites seem to be prone to environmental stress during midsummer, and summer patch has often been linked to stressed turf. To minimize the risk of summer patch, it's helpful to minimize stress on the lawn. Overseeding damaged turf with blends of Kentucky bluegrass cultivars with tolerance to summer patch, or with species mixes incorporating turf-type tall fescue or perennial rye as well as Kentucky bluegrass, can prevent serious outbreaks in the future.
Chemical treatment is an option for summer patch, but the trick is to start early.
Systemic fungicides such as Rubigan, Banner, or Bayleton should be applied first when night temperatures don't fall below 70o F, with repeat applications at intervals of about 30 days until the warm summer weather subsides. This disease is most serious on the creeping bentgrasses that make up most golf greens in Iowa. Recently seeded greens are the most vulnerable, especially where drainage is poor. Scattered, more or less round patches of bronzed to light brown grass, from 4 inches to several feet across, appear in late spring. Some scattered green blades of grass may remain within the patches.