Managing Powdery Mildew on Mature Lilac Hedge

25-year-old white lilac hedge (6×30 ft) developing white mildew. Owner asks about wood ash treatment.

Powdery Mildew Reality

Cosmetic, rarely threatens health. Favored by high humidity and dense growth.

Cultural Suppression

• Prune for air circulation (thin interior).
• Water soil only—avoid wetting foliage.
• Water mid-morning for rapid drying.
• Rake/destroy fallen leaves.

Fungicide Options (verify local labels)

• Bayer Advanced Garden Disease Control
• Monterey Bi-Carb / Erase RTU
• Ferti-lome Dusting Sulfur
• Green Light Fung-Away Systemic
• Ortho Garden Disease Control
• Safer Garden Fungicide
• Spectracide Immunox
• Ortho Orthenex
• Bonide Remedy

Sulfur/copper products often organic-approved. Apply 7-10 days until new growth clean. Wood ash not recommended—alkalinity may worsen conditions.