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Lettuce: Downy mildew

categories: Lettuce Lettuce Diseases Vegetables

revision date: 2022-12-07 12:00

Lettuce leaf infected with downy mildew fungus.
Lettuce leaf infected with downy mildew fungus
Photo by: R.S. Byther

Biology

Lettuce downy mildew is caused by a fungus which survives the winter on wild hosts and weeds. Light green or yellowish areas on the upper leaf surface are in places where the fungus is growing as downy patches on the undersides of the leaves. Affected parts turn brown and leaves die. Older leaves are infected first. This disease is worse in damp, foggy weather and between 43° and 53° F.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

  • Remove weeds from around garden areas.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • None recommended.

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