Fall applied residuals good bet for kochia control

Lentils are the smallest kid on the playground, other pulse crops are their friends and kochia is the bully of them all.

“I lean heavy on kochia,” Mike Brown, agronomy manager at Saskatchewan Pulse Growers, said during last month’s at the Western Canadian Crop Production Show in Saskatoon.

You can find all our 2026 Crop Production Show coverage here.

“It’s kind of one of our biggest issues in pulse crops.”

Kochia is the exact opposite of lentils.

While lentils are slow growing in spring, slow to close canopy and sensitive to saline and early weed competition, kochia is quick growing, resilient in harsh conditions and evolves quickly.

Kochia research

In December, 2024, SPG invested $3.67 million in five projects studying weed science research for pulse crops, two of which focus specifically on addressing kochia.

Of the funding, $2.47 million is dedicated to the Framework for a Collaborative Kochia Management Program in Pulses, which is divided into five research projects to create an integrated management framework of chemical tools alongside cultural and mechanical to reduce herbicide pressures.

These kochia management projects have been underway for the last year, with the first preliminary results coming at the expected in April.

“Kochia isn’t a problem that’s going to be solved with a single product or a single tactic,” said Racquelle Peters, a research assistant for the agronomic crop imaging lab at the University of Saskatchewan.

”It does kind of come back to the idea of a weed management program having a bunch of tools in a toolbox. If we rely too heavily on one tool, we will accelerate resistance and shorten the lifespan of our options.”

Peters has worked on one of the chemical projects, “investigating efficacy of new metribuzin containing co-packs,” which is led by Steve Shirtliffe, plant sciences professor at the university.

She shared the findings of this project’s first year at the Crop Production Show, which found that the most effective kochia control came from fall applied, high-rate residuals, particularly Fierce MTZ, Sencor and Bifecta EZ.

There were three sites for the trials — Saskatoon, Scott, Sask., and Lethbridge — and quite a bit of variability was seen due to weather conditions.

Each site planted CDC Nimble lentils, and preseed treatments were used instead of in-crop. Sencor and Valtera were applied alongside Bifecta EZ and Fierce MTZ:

• Bifecta EZ contains metribuzin, a Group 5 chemical, and Flumioxazin, a Group 14.
• Fierce EZ has flumioxazin and pyrosulfone, a Group 15.
• Fierce MTZ has flumioxazin, metribuzin, and pyrosulfone.
• Sencor has metribuzin.
• Valtera has flumioxazin.

Observations

For the first year, researchers observed the effect of residual herbicides.

“For each one of these, we applied them in the fall at two separate rates, which I’m kind of designating as a min and max,” Peters said.

“These rates that we selected were based on registered rates in the crop protection guide. And then for the MTZ, it was a recommended rate, as it’s not registered in lentil.”

In addition to the fall applications, a spring application of Bifecta EZ and Valtera were trialled.

It seemed like a close game in Saskatoon at the beginning of the trial.

A strong effect from all treatments was measured at seven days after emergence (DAE) and 21 to 28 DAE, but the most consistent results after 56 days came from the max rates of Bifecta EZ, Fierce MTZ and Sencor, which reached the 80 to 90 per cent control range.

Scott showed best control from high-rate Sencor and the spring-applied Bifecta EZ. These two products had the best control compared to the others at the beginning with the seven DAE measurements.

However, while these treatments were the most effective at the final measure, they they rated in the 70s.

Differences were also found at Lethbridge because it had lower kochia pressure than the other locations. Fierce MTZ max rate had nearly 100 per cent control, while Fierce EZ min and max rates were mid-low 90s.

“Bifecta at the fall max held up better than the rest of the non Fierce treatments at about 80 per cent control, but it still did not match the Fierce EZ or the MTZ treatments for seasonal consistency,” said Peters.

Studying results

Lentil biomass was collected to get a better sense of control and treatment effects.

Biomass was chosen over yield due to lack of crop at Scott and too much kochia at Saskatoon. With the lack of crop in Scott, no treatment effect was seen on lentil biomass, but Saskatoon and Lethbridge showed differences.

Most of the fall residual treatments in Saskatoon resulted in significantly more lentil biomass than the untreated.

“We found Fierce MTZ at the high rate, and both Sencor fall rates and both Bifecta rates, to be greater than the untreated,” Peters said.

“These treatments essentially increase biomass five to six fold relative to the untreated control.”

In Lethbridge, fall applied Fierce EZ at max rate had the highest yields.

The treatment’s control results show promise, but there was some effect to the lentils.

Crop injury was generally less than five per cent during the critical weed-free period, but Peters said producers may have to reconsider their level of acceptable plant injury in exchange for reliable kochia control.

She said producers can’t rely solely on chemical control, encouraging them to seek additional methods.

“These residual programs really are a strong foundational player. However, they’re not a standalone solution,” she said.

“We still saw late season flushes of kochia across the sites, enough so that it wiped out our lentil crops, even in those higher rate treatments.”

The 2026 trial protocol has been adjusted with these findings, and the plan is to layer the fall residuals with in-crop applications through tank mixes, three-way mixes and split applications.