summer patch symptoms

Circular, primary symptoms of summer patch on Kentucky bluegrass. Photo: Kevin Mathias, UMD

Updated: June 3, 2021

Susceptible grasses

The most commonly infected grasses are Kentucky bluegrass and fine leaf fescue.

Primary symptoms

  • Initial symptoms on Kentucky bluegrass are roughly circular straw-colored patches of turf that may resemble another turf disease called dollar spot.
  • These patches continue to enlarge with outer edges taking on a yellow or bronzed appearance.
  • The leaf blades turn brown from the tip giving the turf a straw-colored appearance.
  • Healthy turf may survive in the middle of the patches giving a doughnut or frog eye effect.
  • Circular depressions within the patches, called crater pits, may also be present.
  • Fine fescue grasses develop orange or bronze-colored patches prior to the straw color.
severe summer patch infection on Kentucky bluegrass
Summer patch spreading in a Kentucky bluegrass lawn
Photo: Lee Miller, University of Missouri, Bugwood.org

Season

  • This disease usually appears in late June or early July when temperatures above 90F occur.

Environmental conditions

  • This disease is always more severe in the full sun.
  • Daytime temperatures of 90F and soil temperatures of 78F coupled with moisture predispose susceptible turf to this disease.

Management

  • Plant a tall fescue lawn. 
  • Select resistant cultivars when establishing turfgrass.
  • Avoid over-fertilization of turf, especially in the spring.
  • Mow at the highest recommended height.
  • Avoid light frequent irrigations.
  • Reduce thatch when it exceeds a ½ inch in thickness.