Cankers are deformed and diseased areas of tree bark. The directly infected area is usually sunken down, with the surrounding bark cracked and distorted. Initial signs of infection may include new shoots dying and wilting or discoloured leaves. Fruits can also be affected and may rot. Cankers usually have white or red coloured pustules depending on the time of year.
- Apple canker infects apple, pear, mountain ash, beech, hawthorn, poplar and willow. Some varieties are more susceptible than others.
About Apple canker
- Apple cankers occur when the fungus Nectria galligena finds its way into cracks and wounds in tree bark.
- The infection will kill the tissue beneath the bark first.
- The bark around the canker will eventually die back revealing the tissue.
- Damage from pruning can also become infected.
- Fungal spores appear creamy white in the spring and a darker red colour later in the year.
- Spores can move between wounds by wind, water splash, or insect.
- Wet soil exacerbates the infection.
- Mild infections still allow some fruit to set.
- Severe infections can rarely be cured and the tree may die.
- The more infected and exposed areas a tree has, the more susceptible it is to further damage and infections.
Products containing the following chemical ingredients are all effective on Apple canker
- Remove infected branches and twigs, making clean, neat cuts.
- Larger cankers on trunks and thick branches can be cut out, although care must be taken to ensure that all bark showing symptoms of disease is removed.
- Burn all removed infected material to ensure the spores are destroyed.
- Disinfect blades before and after pruning.
- After pruning, apply canker paint to exposed healthy tissue.
- Try to prune only in dry weather.
- When planting new trees, pick varieties with a higher level of resistance to canker.
- Include a spade of lime with the soil when planting a new tree.
- Pruning back leaves and branches to improve the air circulation of older trees will help to stop the disease establishing.
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