Viral Infections In Houseplants

One of the characteristics of a viral infection is distortion of flowers. Tulips are prone to catch viruses. Mottled and streaked leaves, stunted growth and a generally unhealthy looking plant indicate the presence of one or more virus infections throughout the whole plant. They enter the plant during propagation or are transmitted by pests which suck the sap from a sick plant and then carry the virus to a healthy one.

For example, Cucumber mosaic virus can affect many other plants as well as Cucumber, and more than one virus can affect a plant at any one time. Tobacco mosaic virus is particularly virulent and has more than one strain, affecting

virus-in-houseplantVirus infections are caused by tiny particles or organisms (viruses) which enter the plant’s system and change the composition of the plant cells. Taking protein from the plant’s cells, the virus particles grow and spread.


There is no treatment for virus infections. Affected plants should be destroyed as soon as the symptoms are noticed, preferably by burning. Keep suspected plants in ‘quarantine’, well away from the other specimens, and eradicate any pests such as aphids and whitefly which may transmit the virus. Don’t cut away part of a plant and keep the apparently healthy remainder as this is probably also infected.

Recognizing symptoms

Viruses cause a range of different symptoms. Most viruses are named after their primary plant target and have ‘mosaic’ in the name. This refers to the characteristic yellow or pale green mottling or streaking on the leaves. Other symptoms of a virus include distortion of stems and flowers and wilting.

Virus infections cannot be cured and may spread rapidly, affecting plants of the same or a different White fly ( right) can transmit viruses so keep a lookout for them.

Plants to watchviral-infection-in-tomato

Many plants, grown both indoors and outdoors, can be affected by viruses. Tomatoes, Cucumbers and Lettuce are very susceptible, as are Strawberries and other soft fruits. Hyacinths, Narcissus and Tulips and many perennials, including Iris, are also at risk. Certified virus-free plants of some species, such as Chrysanthemum, are available from specialist nurseries, but may themselves eventually become infected if there is a virus around.

Preventing the spread of virus infections

  • Virus infections spread rapidly from plant to plant and cannot be cured by chemical treatment.
  • They can be spread by aphids and other sap-sucking pests.
  • A virus can be transferred from a sick to a healthy plant by a gardening tool or carried on your hands.
  • Keep all equipment, including pots, thoroughly clean. Wash in hot, soapy water, rinse and drain. Also wash your hands when you have a diseased plant. Always use a sterilized potting compost, never soil from the garden.
  • Check plants regularly for pests and take the appropriate action as soon as possible. When using insecticides, follow the manufacturer’s instructions closely and allow sufficient time to elapse between treating and harvesting edible plants.
  • Use only healthy plants for propagation.
  • Don’t use cuttings and offsets from plants showing symptoms of a virus. Even when the parent plant looks fairly healthy, the virus will usually infect all the new plants.
  • Aphids suck sap, and to do so they puncture plant stems and leaves. They can then infect the plant with a virus.



  • Destroy affected plants by burning if possible.
  • Check plants frequently for aphids, whitely and sap-sucking pests, and act against them at once.
  • Use only healthy, virus-free plants for propagation and keep pots, tools and hands scrupulously clean.
  • Buy specially treated seeds which are more resistant to virus infections, when these are available.


  • Dispose of affected plants on the compost heap– the virus will remain in the compost.
  • Be tempted to cut away infected parts and keep the rest of the plant. The whole plant is probably affected and the virus will eventually spread to other plants.
  • Take cuttings from a diseased plant, or use any offsets as they may be diseased.

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