The exact symptoms of different cankers, depends on the plant which is being attacked. However, they generally have patches on the bark which become discoloured, sinking inwards in rings – usually near a wound, leaf scar, side branch or bud.
Fungus which are spread on the wind during spring.
The trees are weaken and extensive die back can occur. Very badly affected trees should be cut down.
Prune out any affected areas and treat with a fungicide. Trees planted in poorly drained, clay soil are much more susceptible, so it is important to try and improve drainage and growing conditons. This can be helped by mulching around the base of the tree with a thick layer of well rotted farmyard manure which is an excellent soil conditioner.