A new study from Cornell University researchers sheds light on how formidable an opponent the invasive pigweed Palmer amaranth is for New York state growers – and offers a way forward.
The plant, first found in New York soybean fields in 2019, has been dubbed the “spotted lanternfly of weeds” for its ability to spread quickly and wreak havoc on crops.
In a paper published in the journal Weed Science, researchers find that some known Palmer amaranth populations – collected from Steuben, Genesee and Orange counties – have resistance to the herbicide, glyphosate, the leading weed control chemistry used in soybean crops. Researchers also confirmed the mechanism for resistance in the populations and identified classes of herbicides that are still effective.
“We can use this information to let our growers know what to expect, so they can make good decisions about how to manage the species,” said Lynn Sosnoskie, assistant professor in weed ecology at Cornell AgriTech. “We want to avoid these population blow-ups that become very difficult to control once they get going.”
“The use of a single strategy or product puts us in danger of reducing the utility of herbicides, very valuable tools,” Sosnoskie said. “We need to be thinking about how to diversify our system of weed management, and how to really look closely at how we could use new strategies and technologies in New York, under our production conditions.”
Once established, Palmer amaranth chokes outcrops and can clog and impede harvesting equipment. Growers in other areas of the country have reported up to 79% reductions in soybean production and 91% in corn.
Sosnoskie’s team found that the New York state populations are 42 to 67 times more resistant to glyphosate than controls; one of the populations is also likely resistant to atrazine, a leading herbicide for corn. While the researchers found that the weed still responds to other classes of herbicides, they warn that simply switching from one herbicide to another is not a sustainable solution.
“We still have sensitivity to several important groups of herbicides, but we have to be mindful that this sensitivity won’t last forever,” Sosnoskie said. “If we don’t use these products responsibly, we could select for resistance to those chemistries, too.”
Researchers and growers are experimenting with alternative and integrated strategies for managing weeds, including changes to crop rotations and the addition of cover crops. They are also testing new technologies; Sosnoskie’s lab is currently researching machines that can detect specific weeds and use electricity, lasers, or targeted sprays to eradicate them, for example.
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