
The caterpillars I'm referencing here are an invasive species called browntail moth caterpillars and they have toxic hairs that cause me (and others) to break out in a severe painful, burning rash a lot like a poison ivy rash.
We've been working on doing in a small patch of Japanese knotweed and discussing having another "Let's kill the invasives!" volunteer event. Last one we had, we got a lot of the invasive honeysuckle pulled out and it hasn't come back in those areas.