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Downy mildew (Hyaloperonos parasitica) affects all types of cole vegetables, and all above-ground parts of the plant are susceptible. Foliage is most commonly affected, and the disease appears as small yellow blotches on seedlings and as angular, yellow spots on the upper surfaces of older foliage. The undersides of lesions may have a sunken appearance, and sporulation of the pathogen will be evident during periods of high humidity. Extensive blighting of foliage is common in severe outbreaks of downy mildew. Cruciferous weeds can serve as a source of the downy mildew pathogen.

Downy midlew lesions on upper leaf surface of collard

(Photo: UKY Vegetable IPM Team, University of Kentucky)

Sporulation of downy mildew on the underside of a mustard leaf

(Photo: UKY Vegetable IPM Team, University of Kentucky)

Management:

• Crop Rotation.
• Planting in areas with good air drainage.
• Weed control.

• Fungicides.

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