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FIG.01 — Downy mildew, diseaseTap to enlarge
Plant part
Leaf · Fruit
P. persimilis
Not stated
DiseaseProblem 02 / 37
Downy mildew
Recorded host crops
Cucumber
Symptoms
Downy mildew is a destructive foliar disease of cucumber caused by the oomycete Pseudoperonospora cubensis. It develops rapidly under humid conditions and can cause severe defoliation and yield losses.
Leaf lesions: Angular, yellow to pale-green spots confined by leaf veins.
Lesion development: Spots become brown and necrotic as the disease progresses.
Underside sporulation: Gray to dark-purple downy growth may develop on the underside of leaves under humid conditions.
Advanced infection: Lesions coalesce, causing extensive leaf necrosis, premature defoliation, and reduced fruit quality and yield.
How to verify
Compare the photos above with the plant, and check the symptom description against the look-alike records below before acting. The source guide does not carry a separate laboratory verification note for this record.
Next step
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Active ingredients
DimethomorphMancozebMetalaxyl/MefenoxamFenamidoneFosethyl AluminiumPropamocarbCymoxanilFluopicolide
Organic active ingredients
Copper sulfateHydrogen peroxideNeem oil
Label matters
Active ingredients below are examples, not universal prescriptions. Confirm the diagnosis; use only products registered for tomato and the target problem in your country; and follow the current label for dose, pre-harvest interval, worker protection, compatibility and re-entry. Rotate IRAC/FRAC modes of action. When symptoms are uncertain, obtain a laboratory or extension diagnosis. Integrated pest management (IPM)—sanitation, resistant varieties, irrigation management, monitoring and biological control—should be the first line of defense.
