Horseweed is one of many winter annuals that has increased across Iowa with the adoption of no-till and a string of mild winters. Horseweed (Conyza canadensis) is a member of the Composite (sunflower) family and is also referred to as marestail. Recently, horseweed has gained considerable notoriety as being the first weed to develop resistance to glyphosate in Roundup Ready® cropping systems, and glyphosate resistance has been reported throughout the eastern United States.
Iowa State University
Hartzler, Robert G. and Owen, Micheal D., "Horseweed -- A weed on the rise" (2006). Integrated Crop Management News. 1231.
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