Leaf Spot - Cool Season Grass
Grass species affected
- Kentucky bluegrass, especially common bluegrass species
- Perennial ryegrass
- Typically during times of cool, wet weather, such as spring
- 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.
- 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.