Broccoli, Cole crops: Downy mildew
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: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- 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
If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.