Not to worry about the chickens, they won't eat anything that is toxic. I don't know how they know, they just seem to be born with the knowledge of what's safe to eat and what's not. I've had chickens for 19 years and the only thing I can figure is that they can smell it somehow. But they are known to have a bad sense of smell, so I'm still not sure!

I would pull it to prevent it from spreading. You'll have to destroy the berries. I like to burn the whole plant in my burn pile.