Powdery mildew

Disease

Fungal growth on leaf surfaces; often white and dusty, sometimes later yellowing.

Often on

Squash, cucumbers, grapes, roses, many ornamentals.

Symptom tags

Powdery or white coating
Distorted or stunted growth
Yellowing leaves

Signs in the garden

White patches on upper or lower leaves that can spread quickly.
Unlike many leaf spots, infected tissue may not always feel wet.

What often helps (general)

Increase airflow (spacing, pruning dense shade).
Avoid overhead irrigation that keeps leaves wet for other diseases; powdery mildew can still occur in dry topsoil conditions.
Remove heavily infected leaves on annual vines if the plant still has time to regrow.

When to escalate

If defoliation reaches fruit sunscald risk or infections start very early in the season, labels and timing matter — ask extension for crop-specific options.