AI yi yi.
My biggest worry about this sort of thing, beyond the chemical warfare is if it could be a pathogen of some kind (baterial, viral, or protozoan). The real worry with that is that it's 1) impossible to verify or test for, 2) essentially impossible to treat for. It's sort of like a greenhouse with bugs and all you can do is hope they die out on their own or that the stock becomes resistent to it.
I hope that this is an isolated incident. Sorry, I realize I've said nothing helpful ... just that I sympathize (and empathize) and wish you good luck!!