Two-spotted spider mite on cucumber
A tiny mite (Tetranychus urticae) feeding on the underside of the leaves and sucking sap out of the cells. In a hot, dry summer it can weaken or wipe out a cucumber crop in a matter of days to a couple of weeks.
Symptom photos
Symptoms
- Fine, pale, yellowish punctures and discoloration on the upper leaf surface (a marbled effect)
- Delicate webbing on the leaf undersides and between the shoots as numbers build
- Leaves yellowing, browning and drying out, starting at the bottom of the plant
- Tiny mites and their eggs visible with a hand lens on the leaf underside
- Stunted growth and poor fruiting
What it does to the crop
- Leaves and whole plants badly weakened and dying early
- A clear drop in yield, with smaller and poorly formed fruit
- Rapid spread to neighbouring plants in dry conditions
What encourages it
- High temperature above 25°C and low humidity
- Prolonged drought with no rainfall
- Dusty, parched surroundings (for example a plot beside a road)
Prevention
- Water and mist regularly to raise humidity (spider mites hate damp)
- Check leaf undersides from June, especially in dry summers
- Remove weeds that act as a reservoir
- Encourage natural enemies — predatory mites and ladybirds
- Remove or isolate badly infested plants quickly
⚠️ 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.
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