Waterhemp, Palmer amaranth, horseweed, morning glory, ragweed and other weeds have become tougher to control as they have developed resistance to herbicides from multiple site-of-action groups.

Corteva Agriscience, Agriculture Division of DowDuPont, and MS Technologies announced the U.S. launch of Enlist E3 soybeans in early 2019.

Enlist E3 soybean trait technology provides tolerance to 2,4-D choline, glyphosate and glufosinate.

MS Technologies and Bayer announced the U.S. commercial launch of LibertyLink GT27 in mid-2018 for commercialization in 2019.

GT27 soybeans are tolerant to glyphosate, glufosinate, and the first HPPD-based herbicide for soybeans. Use of HPPD/Group 27 herbicide on this product is pending Environmental Protection Agency approval.

Bayer’s XtendFlex soybeans are projected for commercial launch in 2020.

XtendFlex soybeans will be tolerant to glyphosate, dicamba and glufosinate. The commercial release is pending on approval by the European Union. China, Philippines and other relevant export partners have already approved XtendFlex soybeans.

Resistance History

The need for multiple weed control options is evident when reflecting on the long history of weeds that have developed resistance to one or several herbicide sites of action.

According to the International Survey of Herbicide Resistant Weeds, the first confirmed report of resistance in Illinois was in 1985 when common lambsquarter was found resistant to atrazine. Multiple resistances were found in kochia samples in Illinois in 1995 and tall waterhemp samples the following year.

Resistance to three sites of action was found in tall waterhemp in Illinois in 2002. Seven years later, samples of tall waterhemp found resistance to four sites of action. Five-way resistance was discovered in Illinois tall waterhemp in 2016.

Since the first findings, other Illinois weeds that have shown at least one instance of herbicide resistance were found in samples including giant foxtail, common cocklebur, giant ragweed, tall waterhemp, horseweed, Palmer amaranth, and smooth pigweed.

The first confirmation of herbicide resistance in weeds in Indiana was found in 1980 when redroot pigweed and common lambsquarter were found to be resistant to atrazine. As was the case in Illinois, multiple resistances were found in kochia in 1995. Most recently, buckhorn plantain samples in Indiana had resistance to 2,4-D in 2016.

Other weeds documented with at least one resistance in Indiana have included common ragweed, Palmer amaranth, tall waterhemp, giant ragweed, horseweed and giant foxtail.

Tom C. Doran can be reached at 815-780-7894 or tdoran@agrinews-pubs.com. Follow him on Twitter at: @AgNews_Doran.


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