Years ago, a wristwatch was known to take a licking but kept on ticking! Well, there’s a weed that does that, too – kochia. Once it gains a foothold, it’s difficult to get rid of it.
We know that kochia thrives in all conditions, but it really likes dry, saline soils, which allows it to outcompete crops. It germinates incredibly early in spring – it’s the first weed up and it’s very frost tolerant. Depending on conditions, a single plant can produce 25,000 to 100,000 seeds. Although its seeds are short-lived compared to other weeds, once it matures and becomes a tumbleweed, it can quickly spread.
But wait, there’s more! Kochia’s herbicide resistance is moving northward from the southern prairies and is growing rapidly. It currently includes Groups 2,4,9 and 14. Yield losses can reach 20 per cent in spring wheat, 13 per cent in canola and field peas and 7 per cent in oats. Pulse crops, such as lentils and chickpeas, are especially vulnerable due to limited herbicide options.
“Kochia knows no bounds,” says Dr. Joe Ikley, a North Dakota State University weed scientist. “While crops struggle during dry years, kochia thrives which compounds its impact. Even a single resistant population can quickly become a larger issue, making control even more challenging.”
Choose your weapons
Combining multiple herbicides with different modes of action, including fall applications of residual herbicides, can suppress early spring flushes of kochia. “Tank-mixes with multiple modes of action are proving valuable in slowing resistance development,” said Ikley.
Rachel Evans, Technical Sales Manager for FMC, agrees. “If growers get a pre-seed herbicide down that has residual control in the spring, that will help with the first flush and goes a long way to get the crop established and competitive,” says Evans.
However, this approach is not without challenges. Dry spring conditions can limit the activation of residual herbicides, so farmers need to weigh the cost of additional applications against the benefits. Careful product selection and rotation of herbicide modes of action are essential to avoid resistance buildup. As Ikley says, “We’re not going to spray our way out of this.”
Getting the most out of an herbicide investment requires paying close attention to sprayer settings.
“With glufosinate, we’ve seen significant differences in efficacy based on factors like droplet size, humidity and carrier volume,” says Ikley.
While tillage remains an option, it’s less favored in dry areas due to erosion concerns. Ikley points out that ‘tickle tillage’ will just tickle the kochia, but more aggressive tillage can be effective where applicable.
Another option is using harvest weed seed control or a seed destructor which damages the weed seed, effectively killing its viability.
Finally, planting competitive crops like winter wheat and hybrid fall rye where possible helps suppress kochia by establishing early and reducing open soil where it can grow. Ensuring rapid canopy closure after planting also limits its growth potential.
“If the ground is covered, kochia doesn’t stand a chance.”
Looking to the future, Dr. Ikley emphasized the importance of stewardship.
“It’s been over 30 years since the introduction of a new mode of action for row crops. We’re relying on old tools, but effective stewardship can extend their utility.” While the challenges are significant, he remains optimistic: “We’re not in a no-win situation yet. Collaboration and proactive management are key.”
So, the war against kochia continues. By mixing herbicide strategies with agronomic practices and new tools, progress is being made. With the right approach, growers can stay ahead and win the battle.
Watch the full webinar here.
