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Lambsquarters Research Yields Unusual Results

Photo courtesy of Iowa State University
Photo courtesy of Iowa State University

One of the most popular online sources for agricultural information in Ontario is CropLine. Sponsored by the Ontario Ministry for Agriculture, Food and Rural Affairs (OMAFRA), CropLine is a weekly podcast covering all kinds of topics of interest to crop farmers. Peter Johnson, cereals specialist for field crops with OMAFRA is the voice behind CropLine, with help from guest speakers. Johnson is an animated, interesting speaker who discusses markets, soils, weeds, diseases and many other crop-related issues. As part of our Agronomy Series, we highlight Johnson’s recent CropLine discussion on lambsquarters research at the University of Guelph. Our goal at Case IH is to provide useful sources of information; we hope this blog and others like it will help you Be Ready for the future. 

Mike Cowbrough has some interesting findings as a result of research at the University of Guelph on common lambsquarters (scientific name: Chenopodium album; Goosefoot Family: Chenopodiaceae). Mike is a weed specialist with OMAFRA and he also teaches the lab portion of a class in weed science for undergraduates at the university when he can. As part of a recent study, he asked his students to apply glyphosate to the uppermost lambsquarters leaf. Over the course of the lab, students would snip off portions of the leaf to see how fast and how far the glyphosate has moved. When Mike asked his students to take a syringe and put glyphosate on the top leaf, his students said, “We can’t.” He watched them try to put a drop of two percent solution on the top of the leaf, and then watched it roll off.

We get lots of samples of lambsquarters shipped in to the University of Guelph where producers think they’re glyphosate-resistant, but they never are. On the other hand, if we get pigweed and other weeds sent in where group-two resistance is suspected, almost 100% are group-two resistant. Still, we continue to have instances where glyphosate doesn’t kill lambsquarters, even though the plant isn’t resistant.

Through teaching this lab, Mike went back to the research and wondered what was going on. The leaf sometimes looks “fuzzy-white” on the surface. Come to find out, lambsquarters is a salt-loving plant that must have evolved close to the ocean, and if it can get calcium or magnesium out of the soil, it will actually uptake it and pump it out through the leaf. You’ll get these little globs on the surface of the leaf of either calcium or magnesium that the plant has exuded. The calcium and magnesium salt ions are so small and so close together that the glyphosate molecules can’t fit in-between, so they roll off the surface. If you take the leaf and rub the salt off, then put a drop of glyphosate on the top leaf, it will stay on the leaf without a problem, and the lambsquarters will be killed.

Some of the time, when we don’t get control on lambsquarters, it’s because the plant has been able to pump enough salt out of the soil to get this “sheen” of calcium and magnesium on the surface, and the glyphosate just won’t stick there to actually kill the lambsquarters.

What do we do to get better control? We’re not exactly sure yet, but this kind of research will help us find the answers, and we congratulate Mike on his findings.

For more information on CropLine, email Peter Johnson at: peter.johnson@ontario.ca, or go to CropLine.

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