Managing Herbicide Resistance

In the past several decades, many Canadian farmers have seen firsthand the challenge of herbicide resistance on their farms.

Herbicide-resistant weeds develop due to the repeated use of the same herbicide group over a number of years on the same field. This typically starts with a small number of weeds developing resistance, and these weeds then spreading across a field and into neighboring fields. These resistant weed biotypes may be resistant to both repeated doses and higher than label rates of the herbicide in question.

There can also be differences in how quickly resistance develops, depending on both the weed and the herbicide. In Western Canada, some of the common resistant weeds are kochia, wild oats, cleavers, and chickweed, and the herbicide group that has the most resistant weeds is Group 2. Resistant weeds can develop within any herbicide group. This is caused by the overuse of that group within too short a period of time.

Understanding herbicides and herbicide resistance can be confusing because different brands often contain the same active ingredient, so simply switching herbicide brands may not help to manage resistance, and could in fact worsen the problem.

What Can Growers Do To Manage Herbicide Resistance?

• Add tank mixes to glyphosate. Glyphosate-tolerant weeds are becoming a major problem in western Canada. When using glyphosate, always add a tank mix partner.
• Rotate herbicide groups. Research has shown that herbicide rotation is one of the best ways to delay herbicide resistance. Check the herbicide label to determine which group it belongs to.
• Use multi-mode of action herbicides. Using herbicide products that have 2 different effective modes of action on the same weed can also help delay herbicide resistance.
• Rotate crops. Different crops will often have different herbicide options, so having a long-term crop rotation can help delay resistance.
• Change cultural practices. Consider cultural changes, such as delayed seeding, tillage, increasing plant stands, and fertility. All of these things can help increase crop competition and reduce weed populations.
• Plan long term. Consider your crop and herbicide rotation over a longer term, not just 1 year. That can help you plan your herbicide rotation at the same time.

Talk to AgraCity first about managing herbicide resistance

AgraCity has the tools you need to help manage herbicide resistance on your farm. We have the largest portfolio of herbicides in the country, providing farmers with affordable high-performance solutions from most major herbicide mode of action groups.

Because AgraCity is not tied to any one supplier or manufacturer, we are able to create new solutions with different herbicide active ingredients from around the world and deliver them right to your farm.