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Powdery Mildew on Magnolia & Hydrangea: Fungicide Options

Confirmation

Silvery, slightly powdery dust on leaves = powdery mildew. Willow death likely unrelated (willows get cankers, not mildew).

Fungicide Choices (Ornamentals)

Active Ingredient	Products	Notes
Propiconazole	Banner Maxx	Systemic, broad-spectrum
Myclobutanil	Systhane, Eagle, Immunox	Systemic, curative + preventive
Sulfur	Wettable sulfur, dust	Organic; avoid >90°F
Triforine	Funginex	Small packages only
Triadimefon	Bayleton, Strike	Systemic
Fenarimol	Rubigan	Locally systemic
Copper	Various	Organic; some efficacy

Application

Spray at first sign; repeat per label (usually 7–14 days).
Cover both leaf surfaces.
Rotate modes of action to prevent resistance.

Cultural

Morning sun, good airflow.
Water soil only.
Remove fallen leaves.

Myclobutanil (Immunox) is widely available to homeowners and highly effective.

Plant Diseases: Preventing and Managing Powdery Mildew on Cucumbers; Identifying and Treating Powdery Mildew on Holly Trees; Powdery Mildew on Indoor Rosemary: Edible-Safe Treatment; Garden Fungus Problems: Powdery Mildew, Black Spot, and Mushrooms in Mulch; Powdery Mildew on Holly: Fungicide Options and Application Timing; Powdery Mildew on Jasmine: Three-Spray Fungicide Schedule; Powdery Mildew on 15-Year-Old African Violet: Cornell University Treatment Guide; Yucca's Natural White Film: Not Powdery Mildew; Powdery Mildew: Identification, Conditions, and Management; Powdery Mildew: Identification, Prevention, and Control

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