I think this is a good idea to fight weeds that can't be dug, like ivy, wisteria, and trumpet vine climbing into trees. Cut them off, and use a paint brush to apply appropriate herbicide. In some cases vinegar might work. I have proposed a similar idea but get jumped on by the anti herbicide campaigners. There are ways to supress weeds, like watering then covering with cardboard. But some--like poison ivy climbing up a building are much better controlled by this method, cut and paint, than with a tank of glyphsate sprayed indescriminately all over the place.
Certainly, using glyphosate is a last resort, but using appropriate herbicides in this manner instead of dousing the country side with it, would solve 90% of the problem of contaminated groundwater.
