It’s no secret that kochia is a huge challenge for growers. This weed scientist explains why.
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.
“Kochia is a big problem, especially in the southern part of the Prairies,” says Charles Geddes, Lethbridge-based Weed Scientist 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.”
Geddes has researched kochia extensively from several different angles in recent years. Here are reasons why kochia can make life tough for prairie crop producers.
Early emergence. Kochia emerges as early as March or April, weeks and weeks before the soil is warm enough to plant into.
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.”
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 seeds per plant.
Efficient seed distributor. Kochia is a tumbleweed, allowing it to disperse its huge seed production far and wide. Under windy conditions, the plant can break off at the stem and tumble through field after field.
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? As Geddes explains, the biology of the plant contributes to the development of herbicide resistance in different ways.
“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.”
Happy to grow 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.
Says Geddes: “It can thrive in those areas of the field where the crop is not as competitive.”
The biology and ecology of kochia are the foundation for the weed’s challenging profile for prairie crop producers. As Geddes sees it, examining and exploiting these factors can also furnish the basis for a rigorous defense.