Apple canker is a fungus that affects apples trees and other types of fruit trees. If it's left untreated, a tree can die from it. Common signs of apple canker are raised bark, sunken sections of bare wood and deformed branches. Broken branches may become more common as they become weaker and the disease progresses. Leafless branches and a sticky discharge from infected areas may also be present.
Watch carefully for signs of infection. Once it is seen, time to do something about it is limited, as signs do not appear until well after the infection has been established.
Cut off any infected branches with clippers, an axe or hammer and chisel so that there is less chance of the fungus spreading. Cut back to the point where you see healthy wood. Otherwise, cutting will do no good, as the infection will remain and continue spreading.
Burn all wood that is cut off. The infected apple tree wood is still capable of producing spores that can travel and infect the tree again.
Apply a fungicide to all cut areas immediately after cutting. Apply it again in the fall after the fruit is harvested, and again after the leaves have fallen.
Rake up all fallen leaves and burn them as quickly as possible. Spores can survive the winter on the leaves, so infected leaves offer a prime chance for the spores to infect the tree again the next year.