The black tips on the leaves at the end of the branches probably had nothing to do with the borer, because this was also evident on the branches below the entry of the caterpillar.
It was unfortunate that the main trunk of the tree was invaded, but of course it was the only section that was large enough in circumference to give the borer sufficient real estate to be protected and live relatively safely. Anything thinner and the branch would have been weakened and could easily break off.
The sugar maples are particularly susceptible to borer infestation and two years ago the one in the pic had to have the same drastic operation performed. It was a much larger tree. A branch was selected that would become the main trunk as was done on this occasion.
