I am searching the internet for solutions to a massive grasshopper invasion.  My trees are planted in a 7 acre field so chickens, guineas, shoes, pruning shears, etc. are out.  Has anyone used either a hot pepper spray or an ammonia spray effectively without damaging the trees?  The other options are a garlic spray (or a mixture of garlic and hot pepper) and Neem Oil.

Some trees have already been stripped bare, so I am looking for a quick solution.

thanks,
~james