Certified GKH Gardening Expert
This treatment will have to consist of preventative maintenance. Once this gets established in the soil, it is quite hard to get rid of.
It is best to get cultivars of apple that are disease resistant. This is the first step. After this, it will be keeping the tree perfectly healthy so that the disease never has a chance to enter the tree.
This article will help with preventing and treating the illness: https://www.gardeningknowhow.com/ornamental/trees/tgen/cankers-on-trees.htm
This article will help with the care of Apple Trees: https://www.gardeningknowhow.com/edible/fruits/apples/apple-tree-planting.htm