Snapdragon: Downy mildew

Biology

Affected plants show stunting and pale yellowish green foliage. Leaves curl in and droop. Leaf undersides may develop a white to purplish fungal growth. The growing point usually dies, and the plant may break off at the base. Downy mildew is caused by a fungus that is favored by cool, wet conditions and/or high humidity. Spores are produced in abundance on infected tissue. Seed transmission may occur, but remains as speculation only.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

• Reduce greenhouse humidity by combination of heating, venting, and circulating air.
• Plant in areas with adequate sunlight and air circulation.
• Space plants to foster air flow.
• Remove and destroy infected plants and plant debris.
• Do not overhead irrigate.

Approved Pesticides

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

• Bonide Fruit Tree and Plant Guard R-T-Spray
  Active ingredient: boscalid, lambda-cyhalothrin, pyraclostrobin [EPA registration number: 4-488]
• Organocide Plant Doctor
  Active ingredient: mono- and di-potassium salts of phosphorous acid [EPA registration number: 71962-1-70179]
• This list may not include all products registered for this use.