Anyone ever use or heard of using Naphthalene Acetic Acid?

I had to dig through some roots of a large crepe myrtle a couple years
ago and have numerous water shoots coming up in that area of the
flower bed and yard. Roundup only kills the foliage and the shoots
reappear after a time.

Anyone familiar with anything to stop this unwanted growth?
--
Hal Middle Georgia, Zone 8
http://tinyurl.com/2fxzcb