Lilac: Powdery mildew

Biology

Powdery mildew is a fungal disease of the leaves. On lilac, it shows typical powdery gray-white growth on the upper leaf surface. Powdery mildew usually occurs fairly late in the season, and does relatively little damage to the plants. This disease is worse in summers with little rainfall and high amounts of fog or cloud cover.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Hand-pick and destroy infected leaves and shoots.
• Gather and destroy any diseased materials from beneath plants.
• Plant species other than Syringa vulgaris which is the most susceptible to powdery mildew.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• Use just before symptoms are expected to occur or when the first symptoms appear.
• Homeowners should not make foliar applications to trees over 10 ft tall.
• Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

• Bonide Fung-onil Multi-Purpose Fungicide Concentrate
  Active ingredient: chlorothalonil [EPA registration number: 60063-9-4]
• Bonide Infuse Systemic Disease Control
  Active ingredient: propiconazole [EPA registration number: 100-773-4]
• Hi-Yield Snake Eyes Dusting Wettable Sulfur
  Active ingredient: sulfur [EPA registration number: 7401-188-34911]
• Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
  Active ingredient: sulfur [EPA registration number: 802-16]
• Monterey Horticultural Oil [Organic]
  Active ingredient: mineral oil/pet distillate light [EPA registration number: 48813-1-54705]
• Safer Brand Garden Fungicide/Flowers, Fruit and Vegetables Concentrate
  Active ingredient: sulfur [EPA registration number: 42697-37]
• Spectracide IMMUNOX Multi-Purpose Fungicide Spray Concentrate
  Active ingredient: myclobutanil [EPA registration number: 9688-123-8845]
• This list may not include all products registered for this use.