Here's one you don't see too often: boring insects taking out a healthy, magnificent Oak Leaf Hydrangae. At first look I thought it was chemical or root damage. Upon further investigation I found the culprit: Boring insects sucking the life out of the prized planting. I elected to recommend pruning the dead areas out and treating the bark and trunk with insecticide to maybe kill a few. Hopefully the insects will go elsewhere or subside and the plant can live....