Answer: Unless your neighbor is willing to work with you to keep it in bounds, all you can do is cut it off where it comes through the fence. A systemic herbicide will do in more than the part that is on your property, and any other herbicide will kill your other plants as well. See if your neighbor is willing to share the expense of a better barrier or will prune or trim ivy that starts to encroach on your property. If friendly means don't do the trick, and hopefully, they will, find out what legal support you have (plants creating a public nuisance?). Hope it doesn't get to that stage! Best of luck.
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