We have a similar issue at two locations near Rocksprings. I believe that the drought last year, combined with the desparation of both domestic animals and wildlife did some real damage to the preferred plants and grasses. Everything that could be grazed was grazed down too much and some of it will be long in coming back. The country looked like a moonscape. The bitterweed, while not being grazed, just took that opportunity to take over. It is a huge problem. The brush cover and rocks do not really allow one to get in with a broadcast sprayer to get much coverage with any herbicide. The bitterweed washes are simply an attempt to limit the spread by vehicles, pretty much an uphill battle if you ask me. I do not know the answer, but agree with you on the problem. I am very interested if someone has an answer..........