Last year I bought some Hybrid AUSTREEs. They are a water loving willow type of tree that grows 6 feet or so in the first year. I'll let you know about the second year. Anyway, they sell (and I've found it again at Gemplers.com) Repellex, which is a latex based repellent that has 30% dried blood. Problem is, it washes off in only a couple of good rainfalls and new growth isn't protected. The stuff is around $114 per gallon, and it dilutes 4-1. Use a garden sprayer to apply. Don't do it on a windy day, this stuff is nasty tasting (handled product, washed hands, still could taste it on my fingers.)

Shawn