As if corn and soybean farmers didn’t have enough to worry about, there’s this: University of Missouri (MU) weed scientists have discovered a waterhemp population that resists six herbicide sites of action.
It all started when farmers in the north-central Missouri county of Randolph reported a population of waterhemp that appeared to resist 2,4-D. MU researchers then conducted field experiments that confirmed 2,4-D (herbicide site of action Group 4) resistance. But they also found the same waterhemp population resisted:
Of the eight herbicides applied, only dicamba (Group 4) and glufosinate (Liberty, Group 10) provided acceptable control, say the MU scientists.
Corteva’s Enlist Weed Control System—still awaiting approval from China for a full commercial launch in soybeans—has a herbicide component that combines a new 2,4-D formulation with glyphosate.
The MU researchers say six-way resistant waterhemp requires a diversified management approach. Rather than relying on glyphosate, 2,4-D, or any other single herbicide, they recommend a variety of appropriate cultural, mechanical, and biological control tactics. For example, rouging weed escapes this summer and hauling them away from the field can help forestall future waterhemp infestations.