Proceedings of the Sixty-first Annual Meeting of the Northeastern ...

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HORSEWEED: FROM OBSCURITY TO THE LIMELIGHT. M.J. VanGessel, Univ. of
Delaware, Georgetown.
ABSTRACT
Horseweed (Conyza canadensis) is a ubiquitous plant species found in
temperate climates world-wide. It infests crops grown under no-tillage production and in
perennial crops. In 2000, plants found in Delaware were identified as resistant to
glyphosate. It was the first report of a broadleaf weed resistant to glyphosate. Since
that time, a number of research programs have had an interest in studying this species.
Based on electronic databases of scientific journals, well over half of the studies listing
horseweed in the title or as a keyword (~60%) were published since 2001. While this
recent interest in horseweed is not exclusive to the presence of glyphosate-resistant
biotypes, most of the ecology and biology based studies of this species cite resistance
as a justification for conducting the trials. Horseweed research since 2001 has become
more expansive and often focuses on horseweed, rather than identifying horseweed as
one of the species present at the experimental site
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