Beet, Chard: Downy mildew
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Biology
Downy mildew can infect any aboveground portion of beets and Swiss chard. The fungus can infect young cotyledon leaves, causing them to appear yellow, mildewed, and to curl downward.
Larger leaves develop pale green to yellow spots on the upper surface, with corresponding white to grayish mildewed spots on the lower surface. These spots may later turn brown and die.
The fungus can survive in infected seed and roots. Downy mildew is favored by cool temperatures and high humidity.
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 resistant varieties. The beet variety ‘F.M. Detroit Dark Red’ is reported to be resistant.
- Plant in well-drained soils and avoid overhead watering.
- Space plantings to provide good air circulation.
- Remove and destroy or discard (do not compost) infected plants and plant parts. Do not leave diseased debris in the garden.
Chemical Management
IMPORTANT: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- Although fungicide applications do not protect perfectly, they are useful when conditions are severe.
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.