What's Happenin' with Plant Toxins

So I sat through** The Happening **last night, and I do have to say that film is sheer genius because halfway through I was ready to kill myself!

But kidding aside, the scene where the goofy botanist says something about a plant that emits toxins that compels a wasp to kill a specific type of caterpiller, that’s was all BS right?

Could such a toxin in theory exist? Inquiring minds want to know.

It’s quite true