Roundup (Glysophate) is absorbed by green parts of the plant and stops photosynthesis. One of the great things about it is that you can spray it on the trunks or above the roots of trees and other woody plants and it won't hurt them as long as you don't get it on the leaves. The bad part of roundup is that it doesn't have any residual action and only works on the plants that were sprayed. Any seeds will sprout and you'll have new weeds.
Pramitol is the go to to if you want long term control. Up to a year following the recommendations on the label. There have been people reporting up to 5 years of control by applying it heavier than the label recommends. The problems with pramitol is that (1) it can move in the soil. I've used it to make a 6" wide strip along chain link fence and ended up with an 18" wide strip. Not terrible but it moves a bit. (2) erosion. Ground with no vegetation will erode. I've see photos of fence lines laying on the ground because the soil around the fence line was washed away. (3) you can't spray it around trees because it is absorbed by the roots. You can spray roundup right up to the trunk and not hurt the tree. Spray Pramitol under the leaf canopy and you'll kill the tree.
I really like Surflan. The only thing it does is stop seeds from germinating. It doesn't kill anything that's already sprouted. It's safe to spray on the ground around trees. I mix roundup with surflan. roundup kills what's growing now and the surflan stops seeds from sprouting. If you spray the mixture around a tree or even on the trunk, it doesn't hurt the tree. It binds to the soil so it doesn't move. It gives up to 12 months control. If you have a lot of rainfall, you may only get 6 months of control. Before round ready corn was a thing surflan was often used on corn as soon as the corn sprouted to prevent any weed competition. It didn't hurt the corn plants, just stopped weed seeds in the ground from sprouting.
