Plant Diseases Fungal, bacterial, viral

Fungi grow best in humid, warm, conditions Fungi cannot make their own food so live on dead or living cells Fungi reproduce by spores that are spread by wind, water or plant pests Fungal spores germinate on the plant surface and grow thread-like hyphae which spread into the cells. The plant cells die as the fungal hyphae feed on cell sap, multiply and reproduce

Common fungal types 1. Leaf Spot (black spot)- black dead areas on leaves, stems & fruit

2. Brown leaf spot

3. Powdery mildew – white spots that join on leaf surface to form a matt. Pumpkins, grapes, roses etc

4. Early and late blight – black dead areas spreading from leaves onto stems and fruits

5. Downy mildew – pale areas on upper leaf surface and soft white growth on lower surface – grapes, onions, cabbage

6. Botrytis (Mould)- rotting of tissue which goes grey/brown and furry – soft fruits

7. Sooty mould – black powdery growth on leaves growing on sugary honey dew from scale and aphids

8. Damping off – seedling stems rot at soil level and fall over – very young seedlings

9. Silver leaf – wood rots and leaves turn silver on surface – stone fruit (cherries, plums, peaches) and some ornamentals

Bacteria infect a wide variety of plants Unlike fungi, bacteria are not spread by wind but are often spread by insects or infected seeds Bacteria symptoms include collapsed tissue or rotting of plant parts

Viruses have no cure so plants must be removed and destroyed Viruses quickly spread through all parts of plants they infect by: Vegetative propagation. If infected plants are used for cuttings the new plants will also be infected Insect pests spread viruses from plant to plant when they suck sap On tools and hands In seeds In the soil

Disease control - accurate disease identification is essential for effective control Two main methods for control of fungi and bacteria are:- Cutting off infected areas and burning them Using special chemical fungicides sprays to kill the spores

Preventing diseases in plants Plant disease resistant varieties. Remove and burn any infected plant parts. Keep tools, containers and hands clean. Keep plants pruned and spaced to allow good air circulation. Control temperature, watering and ventilation to keep greenhouse. humidity low to discourage fungi growth. Make sure soil is well drained. Spray regularly to control pests. Provide suitable shelter from wind. Keep weeds under control. They create damp refuges for fungal spores. Rotate crops to prevent pest and disease build up. Provide good growing conditions to produce strong, healthy plants.