Another glyphosate-resistant weed population confirmed
by Micheal D. K. Owen
February 2, 2005 -  The occurrence of glyphosate-resistant horseweed (Conyza canadensis) has been well-documented and is widely spread in soybean and cotton production throughout the DelMarVa, Mid-South, Delta, Mid-West (Recent publication describes genetics of glyphosate resistance in horseweed). Discussions at the North Central Weed Science Society meeting in Columbus, OH last December included a suspected (and now confirmed) glyphosate-resistant common ragweed (Ambrosia artemisiifolia) population in Missouri and common lambsquarters (Chenopodium album) populations in Ohio that are suspected to be glyphosate resistant.  Recently, the University of Arkansas has investigated a common ragweed population that has been confirmed resistant to glyphosate (Glyphosate resistant common ragweed in Arkansas). 

The need to consider glyphosate stewardship programs is becoming increasingly apparent.  At the forth-coming Weed Science Society of America annual meeting, an open discussion/debate will be convened to provide an opportunity to voice opinions about the use of glyphosate, glyphosate-resistant crops, and the near-term implications these will have on production agriculture.  Information gained from this meeting will be added to the opinions voiced by key commodity associations at the National Glyphosate Stewardship Forum held in St. Louis, Missouri last November.  Notes from these meetings will be compiled into a report which will be made available soon on this webpage, as well as with other sites and formats. 

 Prepared by Micheal D.K. Owen, extension weed management specialist, Department of Agronomy, Iowa State University