WHAT'S NEW WITH BAYER CROPSCIENCE PRODUCTS
ROTATE HERBICIDE GROUP NUMBERS, NOT NAMES, TO HELP MANAGE RESISTANCE
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ew herbicides are launched every year – offering growers improved agronomic packages for better results. But what they don’t often offer is a new chemical mode of action. Awareness of the product’s mode of action, however, is critical when trying to keep herbicide resistance at bay. “Growers don’t tend to think about proactively managing herbicide resistance because there isn’t any immediate impact on their crop by doing so,” says Neil Harker, a research scientist with Agriculture and Agri-Food Canada in Lacombe, AB. “When resistance is relatively minor, they tend to pay less attention to managing it than they could. But once it starts hitting a major weed or a major herbicide near their farm, then they pay attention to the herbicide Group number on the label.” The key factor in most growers’ minds when choosing a herbicide is confidence in the product they are using. And a secondary, but no less important factor, is price. Farther down the list of criteria is mode of action (MOA), but rotating chemistry is necessary to maintain effectiveness of the herbicides available in the market today. Herbicides were officially divided into chemical groups in 1997 based on their mode of action. Of those groups, some, like Group 1 – are contained in many products and brands. Others, like Group 10, have only one product containing that mode of action. It has been five years since a new chemical group – Group 27 – was introduced into the Canadian cereal market, which also represented the first new broadleaf chemical Group for cereals in over 20 years.
Products within the same chemical group do not necessarily control the same weeds. Products may contain a combination of chemistries or have registered tank-mix partners that allow them to control additional weeds. However if the group is the same, the basic chemistry is the same and therefore the risk for developing resistance with successive use increases.
“Growers don’t tend to think about proactively managing herbicide resistance because there isn’t any immediate impact on their crop by doing so” NEIL HARKER Research Scientist, Agriculture and Agri-Food Canada
Rotating chemistry also means more than just rotating brands. Products with different names, from different companies, may share the same MOA. Growers should take care to ensure that changing from one brand of herbicide to another doesn’t result in a continual application of the same mode of action. Harker recommends crop rotation as an important way to manage against herbicide resistance, as MOA can be readily rotated within a varied crop rotation. But he says because of the high returns on a few key crops, rotations are becoming shorter, so the same MOAs are being applied on a tighter timeframe. He adds that short-term economics
can be the biggest threat to resistance management and growers have to work against the desire to go with the same thing year after year. Growers can look to the product labels to ensure their herbicide MOA is rotated annually, as all labels in Canada contain the product’s herbicide group number. There are other sources for making sure a chemical rotation is solid. Provincial herbicide guides all list modes of action, as do websites such as www. weed science.org. Extension support and retail outlets can also offer advice on how best to rotate for excellent results combined with resistance management.
For more information For more information on other agronomic solutions to help manage herbicide resistance, visit www.MixItUp.ca. The website offers current insight into resistance management strategies, and information on how to win the battle against resistant weeds.
FARMFORUM.CA / SUMMER 2013
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