Integrated Approach Needed to Tackle Herbicide-Resistant Kochia Weeds

Herbicide resistance, particularly in kochia weeds, is an escalating issue that demands an integrated approach for effective management. The significance of this topic was underscored during presentations at the Saskatchewan Agronomy Research Update held in Saskatoon earlier this month. Research conducted by the Western Applied Research Corporation (WARC) in Scott, Saskatchewan, has revealed troubling trends in herbicide resistance, marking a shift from previous findings.

Jessica Enns, the WARC research manager, reported that recent field surveys conducted between 2018 and 2021 showed no herbicide resistance in kochia samples. However, she indicated that the current situation is quite different. “We’re actually seeing quite a bit of resistance to saflufenacil. That’s the product called Heat. We found that at a 3X rate in some of these kochia populations, particularly in the Kindersley area,” Enns explained.

The findings revealed resistance levels ranging from 57 per cent to 87 per cent against saflufenacil, with some populations exhibiting resistance as high as 10X. This alarming development emphasizes the need for farmers to adopt new strategies to manage kochia effectively.

Research into Effective Management Strategies

Ongoing research aims to optimise the timing and frequency of mowing kochia. Enns noted the challenge of managing seed production: “If you cut off the top, it’s going to grow seeds from the bottom. What we want to figure out is how are those seeds developing? How quickly are they developing? Are they viable?”

Understanding the viability of seeds produced after mowing is crucial. Enns raised questions about the effectiveness of mowing in June, suggesting that it may contribute to ongoing seed production rather than control. “What we’re really trying to figure out is what’s the best time for farmers to get in there and get this kochia controlled and narrow it down to reduce the amount of seeds that are going back into that seed bank,” she added.

In addition to mowing, alternative methods are being explored, including harvest weed seed control. Josh Lade, a farmer from the Osler area, has implemented a system called the Seed Terminator. This device attaches to a combine harvester and crushes weed seeds before they can germinate.

Lade has been using the Seed Terminator for eight years and has seen significant results. “If we can get these seeds into the combine and through the mill, they’re done. There is an area on our farm that used to be pure kochia. Now we’ve dropped our populations through not just seed terminating but also herbicides,” he stated.

He emphasized the importance of a comprehensive approach, stating, “It’s a full multi-pronged approach. So there’s not just one thing, but I am a firm believer that, especially with kochia, if we can just reduce those populations, it reduces selection pressure for the herbicides.”

The combined efforts of research and practical farming strategies illustrate the critical need for an integrated weed management approach to combat herbicide-resistant kochia. As farmers like Lade share their experiences and insights, the agricultural community can better navigate the challenges posed by herbicide resistance, ultimately aiming for sustainable solutions.