Are Canadian farmers generally doing a good job managing herbicide resistance?
Yes - definitely. Herbicide resistance is a big, complex issue with no single answer or silver bullet. Because resistance is one of those problems you can never completely fix or get rid of entirely, it can be tempting to throw your hands up in the air and give up. But that’s not what Canadian farmers are all about. Instead, farmers have been doing their best to stay ahead of the problem and ensure the tools we do have stay effective for as long as possible.
In a Corteva-initiated study a few years ago, ‘resistance management’ was actually listed as a top-three management consideration behind only profitability and sustainability, and most farmers could name the most common herbicide management practices. When you consider that farmers are not just faced with agronomic decisions but the economic pressures of running a business, I think their efforts in managing herbicide resistance to this point should be commended. Of course, there’s always room for improvement.
Can you provide examples of the types of information that often steer farmers wrong?
Sure. Sometimes you'll see references in advertising or promotional articles where a product is described as having “multiple modes of action.” But this can often be misleading as one active could be for grass control and one could be for broadleaf control, or the individual actives don’t control the same weeds. So, at Corteva, we're taking steps to ensure the information we provide eliminates confusion and raises the level of knowledge. We can't do it on the product labels, but in our support materials we are moving to identify which weeds are actually getting multi-mode of action control, so farmers can be confident in their herbicide decisions. There are a lot of farmers out there doing the right thing with a good crop rotation and herbicide rotation, and we want that to continue.
1. Rotate crops
Crop rotation allows for rotation of herbicide groups, making it more challenging for weeds to develop resistance to repeated use of the same mode of action.
Rotate crops with different seeding and harvesting dates.
2. Mix and rotate herbicides
Rotate from one herbicide mix to another during a growing season and from one season to the next. It’s easy for weeds to become resistant to simple, predictable weed control. Mixing and rotating makes it unpredictable for weeds and creates diversity for your crop plan.
For a mixture to be truly multi-mode of action, both modes of action need to be effective on the same weed species. If you are targeting one species, ensure the herbicides you are using target that weed species.
3. Use recommended rates and timing
Using below-label rates of herbicides can contribute to development of resistance.
Survey your weed populations before spraying so that your weed management is field- and site- specific. Scout fields after herbicide application so that you know how successful you have been in controlling the targeted weeds. This can result in cost savings by reducing herbicide use.
For more best practices to manage herbicide resistance, visit: manageresistancenow.ca.
The best practice is to use glyphosate plus other herbicide products to preserve glyphosate for the long term.
That's a big switch you can very easily make today. Glyphosate-resistant weeds are not common right now and we can help keep it that way by amping up the use of multi-mode of action control, especially for broadleaf weeds. For grass weeds, there are some options available to include pre-emergent grass products.
Why should farmers use recommended rates of herbicides?
Farmers should always use recommended rates and go with the best timing possible, which for most products is that two-to-four leaf stage when the weeds haven’t grown too large and are easier to control. However, Mother Nature doesn't always cooperate in spray season, so you want to check your labels and choose products that have both a wide range of weed staging and a wide range for crop staging. This way, even if you get rain delayed by a week, you get the highest level of control and make no compromises.
What other advice would you give farmers regarding herbicide resistance management?
One of the keys is to try and increase your knowledge in the subject area, because there are lots of opinions out there and some may come with natural biases or other motives. So, always cross-reference your information by checking multiple sources, take advantage of resources like ManageResistanceNow.ca and find a local expert, whether it's an industry representative or a consultant or a retail agronomist, who can give you good advice. Other than that, just keep doing your best.
1State of weed resistance in Western Canada and future outlook, Hugh J. Beckie June 2018