Diagnosing Blackening Grass: Powdery Mildew or Smut

Symptoms and Causes

White/grey patches with tiny white bumps turning black suggest powdery mildew or smut on cool-season turf (bluegrass, rye, fescue). Both are triggered by heavy water/rain, fertilization, and cool temperatures.

Management Steps

• Confirm with local extension tissue analysis.
• Raise mower height.
• Avoid over-fertilizing.
• Water deeply, not frequently.
• Raise soil pH to 6.0+.
• Prune trees/shrubs for light and air flow, or plant shade-tolerant groundcover.
• Systemic fungicide for smut (consult extension); powdery mildew is hard to treat.
• Wait it out and reseed in fall if needed.