Hi TC,
I have a long 1/2 inch drill bit I extended many years ago, so I can drill through the fence down at ground level at the base of the trees and nobody will ever see it, then just poke the copper pipe through the fence and pour in the Glyphosate, hopefully that will do the job. Next problem is I will end up with looking at dead trees because the grubs next door will never do anything about them. They step over anything rather than pick anything up. Always a problem, you can't choose your neighbours, always a lottery