Cucumber · Symptom guide
Downy mildew on cucumber
Angular marks on cucumber leaves in a garden bed are a look-and-compare job. Cited sheets list yellow lesions as observations, not a ranked or confirmed cause. This page does not diagnose.
Cited observations are comparisons—not a confirmed diagnosis. Check the cited sources and local requirements before taking action.
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Illustrative photograph — not identification proof.
Look
Compare the plant in front of you with the cited notes after Other causes. Leaf marks alone do not name a cause on this page.
Other causes
Growing notes live on how to grow cucumber. White coating notes live on powdery mildew on cucumber. Garden-wide looks live on garden pests.
What the sources say — at a glance
One source per card. Facts are not averaged.
Maryland Extension (Maryland)
Yellow to tan angular lesions on a cucumber leaf.
Details and limits (3)
Look
Maryland Extension (Maryland): yellow to tan angular lesions on the lower and upper surfaces of a cucumber leaf. Observation. Cucumber as named.
Look
Maryland Extension (Maryland): symptoms of downy mildew, which can affect cucumbers, squash, melons, and spinach include tan to dull yellow angular lesions (spots) that enlarge. Observation. Cucumber as named.
Limit
Maryland downy-mildew vegetables sheet. Cucumber named — not a diagnosis.
UMN Extension (Minnesota)
Angular yellow spots. Grey fuzz on the underside.
Details and limits (3)
Look
UMN Extension (Minnesota): pale green to yellow spots form on the upper surface of leaves, and later turn brown. Leaf spots are angular and bounded by leaf veins. This is most distinct in cucumbers. Observation.
Look
UMN Extension (Minnesota): dark purplish-grey fuzz forms on the underside of the leaf in high humidity. Observation.
Limit
Minnesota downy-mildew sheet. Cucumber named — not a diagnosis.
Sources differ
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Save the bed in the Field Book so next season is not a guess.
How we know — methodology. Ranges and assertions are cited per source, not blended.