Kochia Weed Control Strategies
It’s no surprise that kochia has been associated with hot, dry weather. Not only does it thrive in that kind of environment, when high winds snap off the brittle stem it turns into a tumbleweed, blowing across the Prairies. In movies it’s become shorthand for drought.
Kochia Loves Hot, Dry Weather
Kochia leaves have soft, thick hairs that protect it from heat. They germinate well in dry ground and even against competitive crops in droughty situations. They have deep taproots that search out soil moisture. That can make a bad drought even worse as kochia mines moisture from the soil.
Saskatchewan Agriculture points to a number of reasons for “reports of increasing tumbleweed populations.” In a recent article about controlling tumbleweeds, the provincial government department suggests wide row spacing, lower herbicide application volumes and the onset of resistance have all led to worsening kochia pressure.
Prolific Seed Production
One of the reasons it’s an increasing problem is that as it tumbles across the ground it spreads seeds far and wide. It’s a prolific seed producer, producing up to 15,000 seeds per plant. But its seeds could also be its undoing.
The good news is that the seeds are short-lived. “Different weed species will have different dormancy levels in the soil seed bank,” says Clark Brenzil of Saskatchewan Agriculture. “Wild oats can survive for five years in sand and loam soils or nine years in clay soils. But 80% of kochia seed that is shed in any one year germinates the next year. The year following, only 3% germinates and the year after that only 1%.”
This means that you can clean up kochia quickly if you stay on top of it. “In short order you can clean up kochia by preventing all seed production,” says Brenzil. “Weeds like kochia, annual brome species, and narrow-leaved hawk’s-beard all have a short life in the soil seed bank. It should be noted that the rare survivor could be a herbicide-resistant individual so it is important to watch for those and pull them out before they go to seed.”
Herbicide Resistant Kochia
University of Saskatchewan researchers say that Prairie farmers should assume that kochia infestations are resistant to Group-2 herbicides. Glyphosate resistant kochia is also spreading across the prairies. Research shows that the best way to manage resistance is to use a product or a tank-mix that contains multiple groups acting on the same weed.
The Agriculture Division of DowDuPont is no longer offering Rynaxypyr® for herbicide control, effective November 1, 2017. Please refer to our affiliate, Dow AgroSciences, at http://www.dowagro.com/en-ca/canada/product-finder to find a list of alternative herbicides.
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