Broccoli, Cole crops: Downy mildew
categories: Broccoli, Cole Crops Broccoli, Cole crops Diseases Vegetables
last review date: 2026-03-15 05:08
Photo by: R.S. Byther
Biology
Downy mildew is a fungal disease typically found on leaves of broccoli, cabbage, and other plants in the mustard family including weeds. Leaves first show pale green to yellowish spots on the upper surface which turn more yellow as they enlarge. The underside of infected areas later develop grayish to white fungal growth.
Stems of broccoli may also be affected, showing spots on the outside and brown to purple streaks internally. Heads of broccoli and cauliflower may be dark brown or black inside, while cabbage heads may show small, sunken, black spots.
Downy mildew development is favored by cool, humid weather.
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!
- Rotate crops yearly.
- Plant in well-drained soils and avoid overhead watering.
- Space plantings to provide good air circulation.
- Remove infected plants and plant parts. Destroy or discard (do not compost) diseased plant tissue.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- Make first application as soon as seedlings appear unless label specifies otherwise.
- Apply at 7-day intervals.
- Copper products may cause flecking damage on the leaves of some cabbage cultivars.
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.