Cucumber mosaic virus

Cucumber mosaic virus (CMV) is one of the most common plant viruses causing yellow mottling, distorted leaves and stunted growth in a wide range of garden plants, not just cucumbers.

Cucumber mosaic virus (CMV) on Aconitum

Quick facts

Common name cucumber mosaic virus (CMV)
Plants affected Many, not just cucumbers
Main symptoms Yellow mottling, distorted leaves, stunted growth
Caused by Virus

What is Cucumber mosaic virus?

Cucumber mosaic virus (CMV) is one of the most common plant viruses and causes a wide range of symptoms, especially yellow mottling, distortion and stunting. Expect damage whenever susceptible plants are growing well in spring and summer.

Apart from cucumbers and other cucurbits, it also attacks spinach, lettuce and celery and many flowers, especially lilies, delphiniums, primulas and daphnes.

For more on how this virus is transmitted, see the Biology section below.

Symptoms

You may see the following symptoms:

  • Yellowish patches or green and yellow mottling on leaves
  • Leaves curl downwards and are distorted and reduced in size
  • Plants are stunted due to a shortening of the internodes (lengths of stem between leaves)
  • Reduction in yields and distorted fruit
  • In flowers white streaks known as ‘breaks’ appear

Control

Non chemical control

  • Apart from the aphid vectors, CMV is easily transmitted on garden tools and gardeners’ fingers. Avoid handling healthy plants after working with suspected infected ones until tools or hands have been washed with soapy water
  • Destroy suspect plants promptly to reduce the risk of transmission
  • Keep the garden weed free. Groundsel and chickweed are particularly likely to harbour CMV
  • Choose resistant cultivars. Courgettes ‘Supremo’ and ‘Defender’, bush marrow/courgettes ‘Badger Cross’, ‘Zebra Cross F’ and ‘Tiger Cross’, cucumbers ‘Bush Champion’, ‘Crispy Salad’, ‘Jazzer F’, ‘Paskia Fi’, ‘Petita’ and ‘Country Fair’ and aubergine ‘Bonica’ all show some resistance

Chemical control

There are no chemical controls available to control virues. The use of insecticides to reduce aphid transmission is not practical.

Biology

Plant viruses share many of the characteristics of those that infect animals, though they do not cross infect (plant viruses only infect plants). Viruses are extremely minute and consist of a protein coat and a core of nucleic acid. They have no means of self-dispersal, but rely on various vectors to transmit them from infected to healthy plants. Once viruses penetrate into the plant cells they take over the cells’ nucleic acid and protein synthesis systems and hijack them to produce more virus. They then require another vector to feed on the infected tissue and carry them to a new host.

CMV is vectored by several aphid species which feed on a broad range of plants and this contributes to the very wide host range of this virus.

The ‘cucumber’ in its name only reflects the fact that cucumber happened to be the plant from which it was first described. In fact its host range is extremely wide among vegetables, flowers and some weeds, though fruit crops are rarely attacked. In some weeds the virus produces no symptoms, but these weeds can still act as a source of infection.

CMV is occasionally transmitted through seed in around 20 plant species.

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