The best wiper for the money is the Spiedel Weed Wiper advertised the the back of the farm magazines. It's a 2 inch PVC pipe with 2 rows of holes drilled in it along the complete length of it, with a heavy canvas cloth tightly wrapped around it and a hose bib on one end (for vaccuum/drip control; the more you open the bib, the wetter the canvas gets and the quicker it drips, for heavy infestation applications; closing the bib down prevents dripping but makes the canvas a bit drier and recharges slower, for less severe infestation applications) and it also has a radiator drain cock on the bottom to drain it at the end of the day. They work really well, much better than rope wick type applicators (which I'm not sure you can even get anymore from what I've seen) and they're pretty cheap. They're sold by Quality Metal Works and I've also seen them advertise a pull type unit on bicycle wheels for pulling behind 4 wheelers. I mounted one on the front of the tractor and had real good luck with it on johnsongrass in cotton fields.
One thing I noticed about smutgrass... an easy and cheap way to get rid of it is to cut it as low as you possibly can with a hay mower. (Disk or drum mower). I had an elderly neighbor that wanted me to cut hay on a 40 acre patch for him, ate up with smutgrass, but did have a lot of good native and stuff too in it. I put new blades on the mower and took everything off about 1/2 inch above the ground, and the following year that field was nearly completely free of smutgrass, and what did come back started out as very small new crowns. A bushhog does nothing to smutgrass because it's pretty tough and the shredder blades just hack the top out of the crown about 2-3 inches high and it grows right back. Sharp blades on a hay mower will zip it off uniformly about 1/2 inch high if you set the machine right and the crowns can't seem to compete or survive very well after that. The hay was pretty decent and the cows eat it, smutgrass and all. The guy's brother told me that he had smutgrass tested one time and it was surprisingly high in protein and decent feed, if a bit low in palatability or digestibility. The cows ate that hay as good as any. Turn lemonde into lemons any way you can, I say... JMHO! OL JR :)