They include stand failures, root abnormalities, bronze wilt, and unexplained boll shed. Most of these have nothing to do with Roundup, though there are some questions about the association of the herbicide with fruit shed. We still do not fully understand the effects of Roundup on RR cotton. The data and knowledge base in terms of variety performance is growing, increasing confidence in some cultivars and diminishing it for others. Yet for several varieties, information is so limited that it is not possible to form a solid opinion.
Conservatism is still the prudent course .
We've always been able to control weeds. Select RR or stacked varieties that show promise in local field trials and plant a few bags. Gain experience in your own fields but with limited quantities. Don't bet the farm on something untested or that might be blatantly unsuited for your conditions.