It’s very clear that when trying to prevent establishment of waterhemp in your field that using multiple modes of action for herbicides and pre-emergent herbicides is important. Expecting to control outbreaks of large actively growing waterhemp with 2,4-D or Liberty in season is not sustainable. The selection pressure for promoting resistance in the weed populations is too risky.
University of Illinois has confirmed 4 populations of waterhemp that are resistant to herbicides from 8 different chemical classes, with Glufosinate (Liberty) being the most recent.
http://www.brownfieldagnews.com/news/university-of-illinois-confirms-first-u-s-case-of-glufosinate-resistant-waterhemp-raising-concerns-for-midwest-farmers
Missouri is the 4th state to confirm Dicamba resistance in Waterhemp populations.
https://extension.missouri.edu/news/mu-weed-science-team-confirms-dicamba-resistant-waterhemp