Are there laws concerning poison ivy?

This is a question concerning the neighbor I recently posted about, we have had a terrible time with poison ivy growing through their fence, for the past 3 years. My son has had to have emergency treatment for it. Well, when we've been having the trouble with them lately from my other question, I mentioned to them that their granddaughter they raise, told me that her grandpa has intentionally been cutting it down to make it grow more so she won't be able to talk to my kids. I expected them to say that was ridiculous, but they said that is what they did, and they said they didn't want to see my trashy kids digging in the dirt in their trashy clothes, they also said they had put the railroad ties along the fenceline, in order to train the poison ivy to grow on our side. He also said he even had to cut down their tree because the poison ivy was growing on it instead of the fence. Do I have any legal options to force them to do something with it? We have spent enough time and $ on it!