Viruses are so minute they can only be seen through an electron microscope. They can cause

 

disorders and disease in virtually any type of plant, though some are more susceptible than others.  

 

Typical symptoms are stunting, distortion, discoloration, striping and mottling of leaves, and deformed flowers. The breaking of flower colour, notably in tulips is caused by viruses.

 

Mosaic virus is a collective name for several viruses that cause leaves to take on coloured patterns (in shades of yellow, red, purple or bronze). This reduces the leaves’ ability to photosynthesise and therefore results in poor performance of the plant.

 

Viruses may be transmitted by handling plants, or through seeds, but most are spread by sap-sucking insects. Aphids in particular are responsible for the troublesome cucumber mosaic virus, which has a wide range of hosts. There is no effective chemical treatment for viral infections.

 

They work right through the sap system, affecting the whole plant.

 

• Lift and burn infected plants. Never use them for propagation purposes.

• Always buy certified virus-free stock when buying plants, specially prone to virus infection, such as soft fruit and potatoes.