Plant diseases

• Tobacco mosaic virus is a widespread plant pathogen affecting many species of plants, including tomatoes. It gives a distinctive ‘mosaic’ pattern of discolouration on the leaves, which affects the growth of the plant due to lack of photosynthesis.
• Rose black spot is a fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early. It affects the growth of the plant as photosynthesis is reduced. The disease is spread by spores of the fungus that are produced in the black spots.
• Common control methods for tobacco mosaic virus include: • removing and destroying infected plants • washing hands and tools after handling infected plants • crop rotation to avoid planting in soil that has been infected for at least two years
• Methods to control black spot include: • not planting roses too close together – to allow the air to flow freely around them • avoiding wetting the leaves when watering – wet leaves encourage the fungal disease • cleaning up any infected leaves from the ground round the roses – to avoid spores spreading • using a fungicide to prevent infection spraying, especially in advance of warm, wet weather