Cankers (Sunken Discolored Areas) on Trees
The answer to your tree problem may lie just below the surface, of the bark that is.
Sunken discolored areas, called cankers, are outward symptoms of problems inside the tree. These cankers can be caused by physical damage from weed whips and mowers, diseases such as fireblight or stress such as extreme heat, flooding and drought.
Reduce these risks and increase your tree’s health and beauty with proper planting and care. Select the most disease-resistant tree suited to your climate, growing conditions and available space.
Plant so the root flare is at or slightly above the soil surface. Mulch the soil with a 2 to 3 inch layer of shredded bark or woodchips. Be sure to keep the mulch a couple inches away from the trunk of the tree.
Water plants thoroughly when needed. Keep the soil of new plantings slightly moist. Water established trees when the top 4 to 6 inches is crumbly and starting to dry.
A bit more information: Find the cause before managing cankers. In general, you will prune these out at least 6 sometimes 12 inches below the sunken discolored area. Destroy the cankered prunings and disinfect tools with a 10% bleach solution or alcohol between cuts. This helps reduce the spread of disease.