There are products that you can use to treat in the tree directly. Just keep in mind that termites are there because the tree is already dead or dying, so be sure to take down dead trees before they cause other damage. You could use Alpine Ant and Termite Foam to spot treat exactly where the galleries are in the tree. This product has a foaming agent to help coat the inside of any voids. Alternatively, you could use Dominion 2L as a spray, again treating inside the galleries directly.
