Herbicide resistance has created an industry of its own, keeping herbicide manufacturers on their toes to create new products to help with this growing problem. And a solution is multiple modes of action.
Herbicide-resistant weeds have been found on the Prairies since 1988 with the discovery of Group 2 resistant kochia and Group 3 resistant green foxtail populations, according to MAFRD. Even though it’s not a new problem, resistance has become an important influencing factor in weed control choices.
Whether the herbicide-resistant weeds have developed here or have been blown in on the wind isn’t relevant to the need for growers to respond by establishing a weed management program that includes a herbicide rotation management strategy.
Developing new herbicide chemistry takes a long time. Discovery through product registration can easily take 10 years. According to Dow AgroSciences, herbicides should be considered a non-renewable resource, and to conserve our available weed control tools, growers need to adopt proactive management strategies.
It is an interesting perspective, to consider herbicides a “non-renewable” resource. Most growers have probably never thought of their weed control with this viewpoint before, but maybe it’s time to shift the perspective.
Dr. Hugh Beckie, Plant Scientist with Agriculture and Agri-Food Canada, suggests that the use of multiple modes of action will be a more cost effective and sustainable approach than herbicide rotation alone.
Dr. Beckie has done extensive research on herbicide resistance and his findings support the practice of using multiple modes of action together in a single growing season as a more effective approach to control. Applying a product with multiple modes of action helps prevent weed escapes by attacking the weeds with different chemistries thereby decreasing the chance that resistant plants will survive and multiply.
For multiple modes of action to be effective, the different active ingredients must provide differing modes of action that control the same target weeds. “If mixing partners of different sites of action do not meet the criteria of similar efficacy and persistence, plus different propensity for selecting for resistance in target species, the effectiveness of mixtures for delaying target-site resistance will be reduced,” states Dr. Beckie.