Journal of the NACAA
ISSN 2158-9429
Volume 1, Issue 1 - July, 2008


Managing Glyphosate-Resistant Palmer Amaranth in Roundup Ready Soybeans

Kichler, J.M., Macon County Cooperative Extension, The University of Georgia,
Prostko, E.P., Department of Crop and Soil Sciences, The University of Georgia


Glyphosate-resistant (GR) Palmer amaranth was confirmed in Macon County, Georgia in 2005. It has been estimated that 87 percent of the soybeans planted in the U.S. during 2005 were herbicide tolerant varieties (NASS, 2007). Soybean producers utilize Roundup Ready systems because of low costs and simplicity. In 2006, two on-farm field trials were conducted in Macon County to evaluate preemergence and postemergence herbicides for the control of GR-Palmer amaranth in soybeans. Preemergence herbicides that showed potential to be used by Georgia soybean growers included Valor, Reflex, Intrro, and Boundary. Glyphosate + Cobra, Reflex, or Ultra Blazer tank-mixes applied postemergence were not effective in controlling GR-Palmer amaranth. The results of both trials suggest that GR-Palmer amaranth will only be controlled using a combination of both preemergence and postemergence herbicides.
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