Snapdragon: Downy mildew
categories: Flowers Ornamentals Snapdragon Snapdragon Diseases
last review date: 2025-07-28 05:05
Photo by: R.S. Byther
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
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
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.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- None recommended
Approved Pesticides
Examples of pesticides that are legal for home use in Washington State are listed below.
The list may not include all products registered for this use.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.