As a non-toxic deterrent, you can't beat a couple of goats. They will eat everything in sight right down to the ground. Especially effective if you can tie them out and let them really concentrate on a problem area. I have both blackberries and English ivy. We no longer have goats, and I've had pretty good luck just clipping them both back to the ground frequently. I'm not too tweaky about getting every scrap out of my yard though, so it's not an all-out battle for me.
