Weeds to Watch - 6
Emily Unglesbee DTN Staff Reporter
Wed Feb 26, 2014 06:59 AM CST

The first confirmed case of glyphosate-resistant horseweed (marestail) bolted out of the gate in Delaware in 2000. U.S. farmers have been struggling to get it under control since, said Bill Curran, Pennsylvania State University weed scientist.

Glyphosate-resistant horseweed was subsequently found in Maryland and New Jersey in 2002, and Pennsylvania in 2003. There are now 21 states with confirmed populations of herbicide-resistant horseweed. So far, horseweed has exhibited resistance to glyphosate, Photosystem Il-inhibitors, ALS-inhibitors, Bipyridiliums and ureas and amides. Resistance to multiple sites of action has been identified in Delaware and several other states.

Curran said the diverse crop rotations ...

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