Dead sections that appear on the main trunk or branches of trees. Cankers, usually, occur from mechanical injuries, fungal, or bacterial infections. This type of disease can quickly cause a lot of harm to the infected tree and kill all of the bark on a main stem or branch; if the main stem or trunk is infected, the entire tree could die. Mechanical injuries can cause an opportunity for wood-rotting organisms to invade the plant. Every step to prevent cankers including proper and regular tree care and maintenance should be taken to avoid cankers.