We have deer problems from hell here and I have tried everything to keep them off my apple trees, Mugo pine and even my hay yard. The ONLY thing that will work positively and permanently is an 8 foot high game fence and even then once in a while a determined deer will jump it. Those ones die in a hail of bullets.
Up here in Candahoovia there is a company called Lee Valley Tools that sells a fishnet type of deer fence that also works for rabbits etc if it is held close to the ground. I have used it and it does work on a small scale but not over a hundred feet or so and it requires some support posts and wire. The good part is that it is almost invisible a few yards away but that means you have to hang some visibility ribbons so animals and people don't blunder into it.
I have tried all the scents, hanging things and noise makers and they only work until the deer become accustomed to them. If it was legal I would run a pack of mean, viscious dogs and finish the whole works of those large whitetailed rats.  
Yeah...I'm fed up with them.  :)
Regards,
Dave.