Powdery Mildew on Weeping Mulberry: Fungicide Program Beats Fruit Tree Spray

White Powdery Coating Isn't Fixed by Combo Sprays

A western Kentucky gardener's weeping mulberry shows white powdery substance on branches since late summer. Fruit tree spray (insecticide + fungicide combo) failed. The diagnosis: powdery mildew.

Why Fruit Tree Spray Failed

Combo products contain low fungicide rates optimized for fruit diseases (scab, brown rot), not powdery mildew. Mildew requires specific fungicides at higher rates.

Effective Treatment

• Fungicides: Myclobutanil, propiconazole, thiophanate-methyl, or sulfur (organic).
• Schedule: Three applications at 7–10 day intervals.
• Coverage: Spray to runoff on all branches, especially undersides.

Cultural Supports

• Prune for air circulation.
• Avoid overhead irrigation.
• Rake fallen leaves (overwintering spores).

Outlook

Powdery mildew rarely kills established trees but weakens them and ruins appearance. Consistent treatment restores vigor. See OSU fact sheet: ohioline.osu.edu/hyg-fact/3000/3047.html