Fungal organisms can help maintain soil fertility by decomposing organic matter. On the other hand, microscopic fungi that can damage and destroy plants include grey mould (botrytis), canker, downy and powdery mildew, rots, rusts, blights and leaf spots. Spores are spread by wind and washed into the soil. Very often they gain entry to a plant through a wound. It is important to keep a sharp look out for signs of attack so that early action can be taken. In general, remove shoots showing signs of disease, destroy infected debris and control with a fungicide spray.
Fungal disease in greenhouses is the result of high humidity combined with poor hygiene. Regularly pick off dead leaves and flowers from plants. Keep the greenhouse surfaces washed with a disinfectant and provide good ventilation. If problems still occur, treat with an approved fungicide according to the disease and plant involved.
• Black spot affects roses.
• Club root is a fungal disease affecting brassicas.
• Damping off attacks small seedlings.
• Silver leaf is a serious disease common on members of the Prunus genus. The worst fungus to have in the garden, however, is honey fungus.