Question
I cut down a Crypt Myrtle tree with appx 4-6" trunk last year.  The stump was ground down at the time.  Now we are getting growth of lots of small Crypt Myrtles.  What can be done to kill the entire root system so I can re-plant in that area ?

Answer
You need to treat the sprouts with a herbicide called Roundup. The Roundup will be taken up by the sprouts and transported to the root system killing the roots. Roundup will kill any green plant it gets on so care will need to be taken to treat the sprouts. I would dip a rag into Roundup and wipe the herbicide on the leaves of the sprouts being careful not to drip it on the grass under the sprouts. I would wear rubber gloves to keep the smell of the herbicide off your hands (it will not harm you but it will smell for a time if absorbed in the skin.) IF there is no grass OR if you do not care if you kill the grass under  and around the sprouts you can spray the herbicide on the sprouts.