Rapidly becoming a major threat to corn and soybean production in the Midwest, giant ragweed is resistant to multiple herbicide sites of action. Thus the reason researchers at the University of Minnesota recently set out to determine the impact of alternative control strategies on both the emergence of this pest and the number of giant ragweed seeds in the weed seedbank.
The researchers evaluated six, three-year crop rotation systems, including continuous corn, soybean-corn-corn, corn-soybean-corn, soybean-wheat-corn, soybean-alfalfa-corn, and alfalfa-alfalfa-corn. They found that corn and soybean rotations were more conducive to giant ragweed emergence. Thirty-eight percent fewer plants emerged when the crop rotation system included wheat or alfalfa.
They also found that adopting a zero-weed threshold can be a viable approach to depleting the weed seedbank, regardless of the crop rotation system used. When a zero-weed threshold was maintained, 96 percent of the seedbank was depleted within just two years.
“Since the ragweed seedbank is short-lived, our research shows it is possible to manage fields infested with giant ragweed by simply eliminating weeds that emerge before they go to seed,” says Jared Goplen, a member of the research team.
To access the full research paper recently published in the journal Weed Science, visit: Seedbank Depletion and Emergence Patterns of Giant Ragweed (Ambrosia trifida) in Minnesota Cropping Systems.