Source: University of Missouri

Brett Craigmyle snipped off shoots of brown and wilted waterhemp one at a time, weighing the plants to determine how dead they really are.

For the University of Missouri weed science graduate student, this is just one step in a research project looking at how best to control herbicide-resistant weeds, which present an ever-escalating challenge in farm fields across Missouri and the country.

The point is to find the best chemical mix that controls weeds and works well with newly developed herbicide-resistant seeds.

"What we're doing here is evaluating different chemistries together, where one herbicide previously had only been used as a pre-emergent burndown and now will be able to be applied after weeds germinate," Craigmyle said. "We spray weeds in the greenhouse at 6-inch and 12-inch heights, rate how much injury they have and then harvest, weigh and dry them to see how much living tissue remains in their system." 

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