USA
December 12, 2013

Waterhemp is one of the most common weed species found in Midwest field crops.  A member of the pigweed (Amaranth) family, this summer annual is capable of producing over a million seeds per plant while significantly reducing crop yields. 

Glyphosate-resistant waterhemp has been confirmed in 12 states.  In Missouri, over two-thirds of the waterhemp populations sampled from soybean fields were found to be resistant to the herbicide glyphosate. 

In the current issue of Weed Technology, a study is reported that sought to identify factors that could serve as predictors of glyphosate resistance in future populations of this weed.  Waterhemp seed samples were collected from 144 soybean fields in 54 Missouri counties in 2008 and 2009 and served as the basis for the conclusions.  Landowners from each survey location were contacted to determine a 5-year history of crop rotation and herbicide use. 

In this study, 94 percent of the glyphosate-resistant waterhemp populations had three field aspects in common: (1) soybeans were the only crop in consecutive years, (2) glyphosate was the only herbicide used for three or more years and (3) the field contained waterhemp showing obvious signs of having survived the previous herbicide application.  These factors provide the best indication that glyphosate-resistant waterhemp is likely to occur in the future.

http://www.wssajournals.org/doi/full/10.1614/WT-D-13-00042.1.

About Weed Technology

Weed Technology presents (1) original research on weed/crop management systems, herbicides, weed resistance to herbicides, and weed biology; (2) reports of new weed problems, weed-related surveys, and new technologies for weed management; and (3) special articles emphasizing technology transfer to improve weed control. The journal is a publication of the Weed Science Society of America. To learn more about the society, please visit: http://www.wssa.net/.

Website: http://www.wssa.net

Published: December 12, 2013