I know this is an old thread to revive but I wish I could go back 3 years when I last posted and tell myself that physical removal is time consuming and expensive. I even bought an $800 rock bucket, but while it works for rocks, does not work well to root out the nopalitos because they can regenerate from a tiny piece. So, long story short, I have experimented with several herbicides of which Remedy Ultra has turned out to work the best for my needs. I finally ran across a recipe that seemed at first to be too expensive but if you figure in labor it's not too bad. It's a mix of 1qt Remedy ($90/gal) to 3qts diesel. Yes, that's a quart not ounces. So a gal of mix will cost you $25. At first I sprayed all the pads as the recipe said but learned that's a waste and not at all necessary. I sprayed about two acres with their suggestion and sure enough the pear were dead and melting down within 2 months. But I also tried spraying just the lower stalk and lower pads on a few as Remedy is meant to be used on mesquite, etc. It works as well on the pear. Really couldn't tell any difference between those I covered completely and those where I sprayed only the stalks and lower pads. It's still not cheap but it's fast and I got results which is what I like. I can't see waiting 2 years to get results as is warned in many of the water mix recipes with Tordon 22K or Surmount. This is spot spraying and on a still day there is virtually no risk of killing other plants so I don't have a problem with the Remedy/diesel mix. I do recommend against using a fine mist spray to conserve because it is more likely to drift that a courser spray. Also, use an all plastic sprayer. Diesel and the galvanized sprayers don't get along too well.
If you want to kill prickly pear, this will do it.