The widespread planting of "Roundup Ready" crops that are genetically engineered to be resistant to the herbicide glyphosate has led to the emergence of glyphosate-resistant weeds in fields in the United States. Of these weeds, the species believed to pose the greatest threat to agricultural productivity is Palmer amaranth - more commonly known as Palmer pigweed - which has infested cotton and soya farms across the southern US and is expected to spread to new areas and crops.
The approach currently adopted to stem its spread has been to apply more and more herbicides, including chemicals which are banned in many countries due to their toxicity. American farmers have also had to revert to agricultural practices used in the 1980s and earlier, such as hand weeding and increased tillage. Such measures will not only push up farm production costs, but give rise to adverse environmental impacts as well.
This paper examines the worrying extent and implications of the Palmer pigweed problem, which the author says shows up the folly of US agriculture's increasing reliance on genetically modified herbicide-resistant crops.