Pests and diseases: Apple canker

Plants affected

• 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.

Treatment

Chemical

Products containing the following chemical ingredients are all effective on Apple canker

• Myclobutanil
• Mancozeb

Organic

• 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.

Prevention

• 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.

Original Article Here