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Cucumber mosaic virus

Cucumber mosaic virus infects hundreds of plants, spread by aphids within minutes of feeding. Leaves develop a yellow-green mosaic and pucker; plants stunt; fruit is small, warty and mottled. There is no cure.

Viral diseases
A courgette leaf with yellow-green mosaic mottling
A courgette leaf with yellow-green mosaic mottling

What it looks like

Mottling and distortion.

  • Patchy light and dark green or yellow.
    Mosaic leaves Patchy light and dark green or yellow.
  • Leaves wrinkle, curl down and stay small.
    Puckered leaves Leaves wrinkle, curl down and stay small.
  • Short, bushy growth.
    Stunted plants Short, bushy growth.
  • Small, mottled, knobbly fruit.
    Warty fruit Small, mottled, knobbly fruit.

How to confirm it

Pattern and spread.

  1. Mosaic pattern

    Irregular light and dark patches, not spots.

  2. Scattered plants

    Individual plants affected, not the whole bed at once.

  3. Aphids present

    Aphids on or near the crop.

What to do

Remove and control aphids.

  1. Remove infected plants

    Pull and bin affected plants promptly.

  2. Control aphids

    Keep aphid numbers down, especially early.

  3. Wash hands

    Wash hands and tools after handling infected plants.

  4. Grow resistant varieties

    Resistant cucumbers and courgettes are available.

Prevent it next time

  • Remove weeds that carry the virus.
  • Cover young plants against aphids.
  • Buy healthy plants.

What not to do

Do not compost infected plants, or save their seed.

In the growing guides

Where the guides mention it, with plant-specific advice.

Sources

  1. Cucumber mosaic virus, Royal Horticultural Society
  2. Viruses of vegetables, University of Maryland Extension