Cytospora is a fungus that causes lesions or sores on trees. Some types cause sunken areas that may look rotted or brown. It occurs on woody plants or parts of plants that are weak or stressed such as those recently transplanted or those that get wounded in some way.
Scale insects weaken trees and that in turn causes susceptibility of canker.
Control that pest if you notice them. Trees affected include several hardwoods such as ash and birch, softwoods such as spruce, and some fruit trees such as apple or peach. Control canker by making sure the tree keeps a balance of water and nutrients. Desperation for water and food will weaken the trees and eventually bad things happen. In drought areas, water as much as you can and deeply.