I'm afraid we're either going to need more information or a photograph, preferably both. When you say Salix, which Salix variety is it precisely? And I'm a little confused by your saying the 'tips' are brown, but the new growth is fine - 'tips' at the end of branches is where most of the new growth occurs, so what do you mean by 'tips'? Tips of the older leaves? Tips of old branches?