Bacterial diseases of plants are not as common as fungal diseases but they can cause dramatic leaf spotting a stem dieback in wet weather.
Identify the problem
Bacterial diseases cause leaf and fruit spotting similar to fungal diseases such as black spot, shot hole and other leaf spot diseases. Bacterial leaf spots are typically angular in pattern and are ringed by a slimy or water-soaked ring of leaf tissue.
Some cause stem dieback where stems dieback from the tip. The stems blacken and dry up leaving withered leaves and bacterial canker causes gummy sap to extrude from stems.
Prevention and Control
- Chose healthy plants that are resistant to disease.
- Do not water the leaves of plants; water the roots if the plants need watered.
- Apply copper sprays as protection and in periods where conditions are wet for long periods.
- Do not apply fertiliser in autumn as this promotes soft new growth at a time when bacterial diseases are prevalent.
- Cut out dead material (sterilise cutting equipment with methylated spirit or dilute bleach between plants to prevent spread).
- Clear away and burn all leaf litter under or around affected plants.
- Carry out a Winter Spray Treatment.