Officially, there are now 31 weed species around the world confirmed as having biotypes resistant to glyphosate. Over the past four years, new cases of glyphosate resistant populations have been confirmed in Argentina, Australia, Brazil, Canada, Greece, Italy, Japan, Mexico, New Zealand, Portugal and the USA. This is, no doubt, just the tip of iceberg, because once a species has several resistant populations in a region, a new one is no longer a surprise and the emphasis shifts from confirming new outbreaks to fighting the problem.
First confirmations of glyphosate resistant populations of six new species have been added to the list of resistant species maintained by the International Survey of Herbicide Resistant Weeds1 since the last update by The Paraquat Information Center (Table 1).
Table 1. New species of glyphosate resistant weeds confirmed since 2011.