I was about to click out when I saw your ref to "bamboo" like appearance. Washington state just put out a warning on "knotweed" whose stalks resemble bamboo (within the month in the newspapers). They are concerned and offer help. Try a google search.
Wow. That must be some kind of roundup. Around here Roundup does not even make simple broadleafs look that bad for quite some time. Honey suckle just turns a bit yellow and then laughs it off.