Went up to the Roaches last night and warmed up on Maud's Garden. I have never seen a route in such a state - every hold and every step was covered with dust, dirt and bits of dried grass. It reminded me of a stretch of road when cattle have crossed from one field to the next. It only went as far as the big shelf, nothing on the upper part. No other routes I saw were in the same condition.
Given it was only the one route I suspect it's a big party that's been going up and down it. It could also be general use, although why just Maud's Garden I'm not sure.
Whoever it was, learn to clean your shoes! The route is polished enough.
Probably a contributing factor but the fact remains that popular slabby gritstone routes often get coated in crap from endless pairs of trainers. Organised groups should ensure that their top-roped clients are aware of crag etiquette: clean your boots/trainers before climbing!
We were bimbling up some easy routes on the skyline and every ledge we encountered was covered in similar stuff. It made the whole thing feel a little less secure than usual. Probably a combination of winds and the very dry ground above depositing debris. As Jon says, the low angles sections will just hang on to it.