I've hung strings of computer discs in my mango tree to deter the critters. They are highly reflective, and cheaper than pie pans. Move around lots in the breeze.
I also have a motion detector sprinkler that works wonderfully, but you must place it somewhere that the leaf motion with the wind doesn't trigger it every few seconds, or you'll use a lot of water scaring off your deer. It's great for an open area as you can aim it high enough so it will 'see' deer but not leaf movement. But if there are trees or taller plants within it's range it's not going to work. It also works at night, but I can't use it against my raccoon visitors because then the cat gets sprayed and comes in pretty mad.
