🥒 Cucumber How hard it is to control: ★★☆☆☆ 2/5

Powdery mildew of cucurbits on cucumber

In field conditions occurs commonly on various cucurbit species, including cucumber, especially in greenhouse crops.

Symptom photos

Powdery mildew of cucurbits — Leaves densely covered in white, powdery growth — Leaves densely covered in white, powdery growth Photo: Nieznany, licence CC BY-SA 3.0

Powdery mildew of cucurbits — Close-up — dusty white fungal growth on the leaf surface — Close-up — dusty white fungal growth on the leaf surface Photo: Nieznany, licence CC BY-SA 3.0

Symptoms

Initially small, round clusters of white powdery coating on upper leaf surface
Clusters enlarge and merge together
Coverage of significant part of leaves with white coating
Heavily infected leaves dry and die

What it does to the crop

Reduction of assimilation surface
Drying and die-back of heavily infected leaves
Plant weakening

What encourages it

Dry and warm weather
Optimal temperature 20-27°C
Relative air humidity 50-80% (low humidity <40% inhibits development)
Nitrogen over-fertilization

Prevention

Cultivation of resistant or tolerant varieties
Weed elimination (can be hosts for pathogen)
Avoiding too dense planting/sowing of plants
Conducting rational fertilization
Thorough removal of plant debris after cultivation ends

⚠️ Before you reach for a spray

This atlas is informational and still growing — different diseases can look almost identical. Confirm the diagnosis and read the product label before applying any plant protection product. If you are unsure, ask your local extension or advisory service.

Keep the disease atlas with you in the garden

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