Morning glory is tough to kill with a spray because the waxy leaves repel herbicides. The best control is to get down low and cut the vines off at ground level. They will return of course so you must cut again and then again. This will starve out the roots if you keep the top growth cut. Sometimes a pair of scissors works best to keep cutting the top growth down to ground level. I have found it takes at least 3 pruning attacks and the second and third cutting must be when the new growth is just a few inches tall so the sprouting weeds cannot use their new foliage to make food for the roots below. In a large area a string trimmer can do the job. This method works for horse tail weeds as well as both of these weeds cannot be controlled by simply pulling them up. Pulling will just stimulate the roots to break off and make more plants. Another solution is to move. Keep growing - but not morning glory - Marianne Binetti