Bark issues are a copper deficiency. Plants use copper to make lignin which is the material for making the trunk. Copper sulfate is available at garden centers and online. I would mix 1/8 tsp per gallon of water. Add molasses for better absorption (one tbsp per gallon.) and spray on the trunk. It will absorb very nicely. Do this once or twice a month until you see improvement. The deficiency is quite severe judging by the deeply split bark. Bill