Powdery Mildew on Sage: Baking Soda Spray Recipe

Your sage's persistent powdery mildew in full sun (Pacific NW) is common—sage is highly susceptible, and coastal humidity fuels it despite sun.

Baking Soda Spray (Preventive + Early Curative)

Recipe:

• 1 tablespoon baking soda
• 2.5 tablespoons horticultural oil (or vegetable oil)
• 1 gallon water
• 0.5 teaspoon castile soap (emulsifier)

Method: Mix oil + soda + soap first, then add water. Shake constantly while spraying. Cover all surfaces. Repeat every 5–7 days.

When to Use Commercial Fungicide

• If baking soda fails after 2–3 applications.
• Myclobutanil (Immunox), propiconazole (Infuse), or sulfur (Safer) work well.
• Rotate modes of action if spraying regularly.

Cultural Tips for Sage

• Full sun, excellent drainage (gritty soil, raised bed).
• Space plants for air flow.
• Water at base only—never overhead.
• Harvest often—removes infected leaves, stimulates new growth.
• Replace plants every 3–4 years—sage gets woody and disease-prone.

Baking soda works best as a preventive. Start early next spring.