The torch you are referring to is something we use to burn off pasture that has been carefully plowed around to prevent the flames from reaching a hedgerow/weeds/trees/brush. I think it would be extremely dangerous to torch the weeds along the fence line. Fire also damages posts and galvanized wire fence, too. Chemicals are the method of choice, but HD weedeaters will also do the job.
Thanks- that's helpfu to knowl, and I wondered as much. I should have added that I was planning to do this only in my paddocks (no grass- sand footing) where I get pesky nettles in the fenceline not my pastures, where the weed-eater works great. It's tougher to get the weed-eater into my paddock fencelines.
Since I have lactating mares and an infant myself, application of nearly all of the commonly used chemicals for weed control is no longer an option on my place.