When a Harvard professor accidentally let Gypsy Moths loose in the 1860s, he didn’t realize he was releasing a scourge that would plague New England forests for more than a century. Nothing could stop the moths except a controversial method of wildlife management called biocontrol. It’s the scientific version of “fighting fire with fire”: eradicate an invasive species by introducing another invasive species. Since then, there have been lots of biocontrol success stories, but also a few disastrous failures. In this episode, we ask whether biocontrol is the best--maybe the only way--to combat invasives, or if it’s just an example of scientific hubris.