How to spot it

Yellow, angular patches on top of the leaves, boxed in by the veins, with gray-purple fuzz underneath. It comes in cool, wet, or humid weather. Basil turns yellow with dark fuzz below.

What it does

Leaves brown and die fast; cucumber vines can collapse in a week or two.

What to do now

• Remove and bag infected leaves or plants.
• A copper spray can slow it on cucumbers and melons if you start early.

Keep it away next time

• Grow resistant varieties ("DM" on the seed packet), especially cucumbers and basil.
• Water the soil, not the leaves, and in the morning.
• Space plants so leaves dry quickly.

Helpful supplies

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Plants it affects

Every plant in the cabbage family (brassicas).

See also