Damp and cool weather create the perfect environmental conditions for fruiting vegetables or cucurbits to develop downy mildew. These conditions also favor the development of Phytophthora, which means potentially simultaneous disease threats to the roots, leaves and fruit.  

Downy mildew causes the development of green to yellow spots on the top of the leaf surface and white, fluffy growth on the underside. If left unchecked, severe infection can kill leaves and result in defoliation. Meanwhile, Phytophthora can attack the roots and fruit of plants, damaging plant health and fruit quality.

Marty Wigglesworth, Syngenta agronomy service manager for the eastern U.S., discusses the risk of downy mildew and Phytophthora in vegetables.

Disease management tools

These pathogens continue to evolve, making proactive management vital. Resistant cultivars are a key management tool, and an effective fungicide program also plays an important role.

When conditions favor the development of downy mildew and Phytophthora, Syngenta recommends application of Orondis® Ultra fungicide. Orondis Ultra features 2 active ingredients that are highly active against Oomycete diseases like downy mildew and Phytophthora. Revus® fungicide and Actigard® 50WG plant activator are good rotational partners for season-long disease management.

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All photos are either the property of Syngenta or are used with permission.