Lilac Powdery Mildew: Benign Fall Fungus

White powdery coating on lilac (Syringa) bark in fall is powdery mildew — a nearly universal, cosmetic, non-damaging late-season fungus.

Key Facts

• Ubiquitous: Most lilacs have it by September.
• Cosmetic only: No long-term health impact.
• Seasonal: Disappears with leaf drop; doesn't overwinter on bark.
• No treatment needed: Fungicides now are pointless.

If Concerned

• Take sample to extension for confirmation.
• Improve air circulation via pruning next spring.
• Choose resistant cultivars for new plantings (e.g., 'Miss Kim', 'Palibin').

What It's NOT

• Not scale insects (those are bumps, not powder).
• Not fatal canker or systemic disease.

Ignore it — your lilac will leaf out beautifully next spring regardless.