Higher moisture in CA growing regions can lead to higher pressure from downy mildew in leafy vegetable crops. Damp and cool weather creates the perfect conditions for downy mildew to develop on leaves.

The pathogen Bremia lactucae causes downy mildew. Wind carries spores between plants, and cool temperatures and moisture on the leaf surface create the environment for this disease to spread. This disease causes leaves to develop green to yellow spots on the upper side and white, fluffy growth on the lower side. When severe infections are left unchecked, they can kill leaves.

Chris Clemens, Syngenta agronomy service manager for the Western U.S., discusses the increased risk of downy mildew when there is high moisture.

Managing downy mildew

This complex pathogen continues to evolve and generate new races, making proactive resistance management vital. Resistant cultivars are a key management tool, and it’s also important to rotate fungicide sites of action.

When conditions favor the development of downy mildew, Syngenta recommends Orondis® Ultra fungicide for excellent control of the disease. Orondis Ultra features 2 active ingredients that are highly active against Oomycete diseases like downy mildew. Revus® fungicide makes a good rotation or tank-mix partner, while Actigard® 50WG activates the plant’s natural defense systems to protect itself against diseases.

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