It’s no secret that kochia is a massive challenge for growers, and that challenge is no longer confined to the southern Prairies. Once considered a southern issue primarily, kochia is now moving north, expanding its footprint as climate conditions, cropping practices, and resistance pressures evolve.
By the time you head to the fields to start seeding, it’s already too late. Kochia has defied cool spring soil temperatures and emerged from the ground with a significant head start on the crop you’re planting. From there, the whole growing season can be a struggle, whether you’re farming in traditional kochia hotspots or regions that are now seeing it for the first time.
“Kochia is a big problem, especially in the southern part of the Prairies,” says Charles Geddes, Lethbridge-based Research Scientist focusing on Weed Ecology and Cropping Systems with Agriculture and Agri-Food Canada. “That’s in part due to herbicide resistance, but there are also several unique characteristics about the biology of kochia that allow it to thrive under the growing conditions of the southern Prairies.”
What’s becoming increasingly clear is that many of those same biological advantages are allowing kochia to establish and persist farther north, challenging assumptions about where this weed “should” be a problem.
Geddes has researched kochia extensively from several different angles in recent years. Here are six key reasons why kochia continues to make life difficult for Prairie crop producers:
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Early emergence. Kochia emerges as early as March or April, weeks and weeks before the soil is warm enough to plant into. This early start gives it a competitive edge—one that’s proving just as effective in cooler, more northern environments.
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High degree of genetic diversity. While kochia plants might look similar to the naked eye, inside you’ll find extensive genetic diversity. “Kochia can be as genetically diverse within a single field,” says Geddes, “as between two fields that are far apart on the Prairies.” That diversity increases the odds that some plants will survive changing conditions, new environments, or herbicide applications, helping kochia adapt as it spreads into new regions.
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Prolific seed producer. Kochia can produce 20,000 to 30,000 seeds per plant on average, with the potential to produce up to 100,000. Even low-level infestations can quickly turn into widespread problems.
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Efficient seed distributor. Kochia is a tumbleweed, allowing it to disperse its considerable seed production far and wide. Under windy conditions, the plant can break off at the stem and tumble through field after field, crossing fences, ditches, and field boundaries with ease. This mobility is a significant reason why kochia is appearing farther north, even in areas where it was rarely seen a decade ago.
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Susceptible to resistance. Herbicide-resistant kochia has become one of Prairie farmers’ most pressing agronomic challenges. Why so much resistance in this one particular weed? “Kochia has a period of forced outcrossing that’s followed up by self-pollination,” he says, “so that’s how we see the transfer of herbicide resistance traits.” That combination accelerates the spread of resistance traits within fields and across regions.
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Happy to grow almost anywhere. If you’re counting on abiotic stresses like heat, drought, or salinity to keep kochia in check, sorry. When hot summer days stress crops like wheat, kochia soaks up the heat and keeps on growing. “It can thrive in those areas of the field where the crop is not as competitive,” says Geddes. As kochia pushes north, this adaptability is proving to be one of its most dangerous traits.
The biology and ecology of kochia are the foundation of its challenging profile for Prairie crop producers. As Geddes sees it, examining and exploiting these factors will also be key to building more effective, long-term management strategies as kochia continues its march across the Prairies.