Infectious diseases in plants

• What is Tobacco mosaic virus (TMV)?

  TMV is a widespread plant infection and it infects a number of different plant species including tomatoes. It causes the leaves to discolour in a mosaic pattern. Because of the discolouration, the rate of photosynthesis is reduced, meaning the growth of the plant is reduced.
• What is rose black spot?

  It is caused by a fungus and it causes the leaves to develop purple or black spots. The leaves often turn yellow and fall of. Rose black spot causes the rate of photosynthesis to fall and this reduces the rate of growth. Rose black spot can be spread by water or wind.
• How do we treat rose black spot?

  By spraying plants with fungicides.

  By removing the infected leaves and destroying them.
• What do Aphids do to plants?

  As well as microbial pathogens, insects can infest a plant. Aphids are a common example of these seen in UK gardens and greenhouses. In particular, they infest roses and tomatoes. They are found in large numbers on new shoots, from which they suck sap. This reduces the growth rate of plants and can eventually kill them. Aphids are eaten by ladybirds, so gardeners often try to cultivate these in their gardens as a natural way of reducing aphids.