Sycamore Powdery Mildew: Fungicide Options, Tree Spraying Optional

Diagnosis

Thick white fungus on sycamore leaves spreading to peony/boxwood = powdery mildew. Host-specific strains but same management.

Fungicide Choices

Application Strategy

• Peony/boxwood: Spray now (accessible).
• Sycamore: Hard to spray; leaves dropping soon. Often unnecessary—mildew rarely harms mature trees.
• Timing: Start at first sign; regular schedule; more frequent in cool/damp.
• Coverage: Both leaf surfaces; use spreader-sticker.

Cultural

• Thin canopy for airflow.
• Water soil only.
• Remove fallen leaves.

Many trees tolerate annual mildew with no health impact. Focus spray on valuable understory plants.