Leaf Spot - Cool Season Grass

Dark colored spots on grass leaf blades are Leaf Spot, it can be treated with proper mowing.

 

Grass species affected

  • Fescues
  • Kentucky bluegrass, especially common bluegrass species
  • Perennial ryegrass

Disease occurrence

  • Typically during times of cool, wet weather, such as spring

Symptoms

  • Small lesions on leaf blades.
  • Dark-colored spots that eventually turn light tan, but the margins remain dark brown.
  • The grass turns brown or straw colored and eventually dies, possibly in patches.

Management

  • Mow the grass high, 2.5 to 3 inches, to provide leaf blades greater surface for increased photosynthesis to produce food.
  • Mow unaffected areas first and diseased areas last to avoid infecting areas of healthy lawn.
  • Collect and dispose of grass clippings in the garbage when leaf spot is present.
  • To avoid spreading the fungus, after mowing, clean the mower blades by rising with water and drying with a cloth.
  • Avoid excessive nitrogen when fertilizing in spring to avoid rapid growth. The nitrogen in Milorganite is released slowly and can be used safely throughout your fertilization schedule.
  • Continue your fertilization schedule even if an area is straw-colored to encourage recovery and healthy turf.
  • Aerate and dethatch your lawn as recommended, which also promotes deeper, healthier roots.

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Dark colored spots on grass leaf blades are Leaf Spot, it can be treated with proper mowing.