This hole in my Tydemans Late Apple shows a puriri larvae is in occupancy. That vertical scar and diamond shaped hole is the giveaway. They drill into the trunk, eating the wood as they go.
Get onto it and save your trees with this very simple (and kinda fun) solution.
You need three things
Fill the syringe with kero and shoot it into the hole.
Plug it with blutak.
Sorted.