I use Remedy and swear by it for killing mesquite and oaks. I mix it with water as a foliar. I expect I would go with diesel and spray the trunk area around the water. If you miss any part of the trunk, it won't die. I haven't sprayed this year but I seem to recall the ratio is 3 or 4 to one for trunk applications.I contacted Kelly Duffie by E-mail and followed his directions, especially concerning the correct surfactant. He works for Estes Chemical and I found the counter guys there to be very knowledgable. BTW, I have come to the conclusion that oaks and mesquite are not trees but weeds. It takes several herbicide applications to finally kill them. Tougher than Johnson grass.