White Coating on Kentucky Bluegrass: Likely Powdery Mildew, Treat with Horticultural Cornmeal or Baking Soda

Homeowner's sister has yellowing grass with prior white coating in strips near house and evergreens. Asks if soil acidity or concrete foundation is cause.

Diagnosis: Powdery Mildew

White coating = powdery mildew (fungus). Favored by shade, poor air flow, humidity. Strips near house/evergreens match.

Organic Treatments

1. Horticultural cornmeal: 10–20 lbs/1,000 sq ft, watered in. Feeds Trichoderma which attacks mildew.
2. Baking soda spray: 4 tsp (1 heaping tbsp) per gallon water. Spray top and bottom of blades. Alkaline pH inhibits fungus.

Cultural Fixes

• Prune evergreens for light/air penetration.
• Reduce nitrogen fertilizer.
• Water early morning only.
• Soil test for pH—concrete can raise pH locally, but mildew prefers shade over pH.

Treat the fungus, improve environment, and grass will recover.