Today 
Left unchecked, canker can gradually spread to affect whole branches and sections of trees. Severely-infected old trees may be beyond rescue, while young trees are vulnerable to infection, particularly where other susceptible trees are growing in close proximity. Where trees are suffering stress as a result of drought or waterlogging, they may be more liable to infection. Canker may also infect fruit, so they rot on the tree before harvesting or when in store. If your trees have suffered this in the past and you're considering replacing them, choose canker-resistant varieties such as the apples 'Grenadier', 'Laxton's Superb' and 'Newton Wonder', and the pear 'Concorde'.
Solution
Organic
Use secateurs to cut out all infected growth. Infected branches show dark staining of the creamy coloured wood inside, so prune back to healthy wood that shows no sign of staining. Carefully slice away cankers on large branches and trunks using a sharp knife. Afterwards, sterilise your knife and secateurs with methylated spirits to avoid cross-contamination. Where canker is a problem, choose resistant varieties.
Chemical
Spraying fungicides featuring myclobutanil and mancozeb during spring and summer will help control the spread of the disease. Bordeaux mixture can also be applied after fruit harvest and during leaf fall.
