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Developing decision support tools for effective herbicide

Ensuring multiple effective modes of action during herbicide applications.

March 8, 2023  By Donna Fleury

Herbicide being applied in a wheat field. Photo courtesy of ten03 /adobe stock.

Herbicide-resistant weeds are increasingly a challenge for weed management in Western Canada. Using multiple effective modes of action (MEMOA) during herbicide applications is a key strategy for both managing and delaying the evolution of herbicide-resistant weeds. However, this can be quite complicated and researchers are working on potential tools to help make herbicide planning and management decisions easier and more informative. 

“One of the components of managing cropping systems for herbicide-resistant weeds is effective herbicide tank mixing, herbicide layering and understanding multiple ingredient products,” explains Breanne Tidemann, research scientist with Agriculture and Agri-Food Canada in Lacombe, Alta. “However, it can be quite challenging to assess whether a herbicide management plan and certain tank mixes are really providing MEMOA during herbicide applications. To try and address these challenges, we are working towards developing a decision support tool to aid growers in determining what multiple ingredient products or tank mixes would constitute MEMOA for target weeds in their field.” 

Tidemann adds that the key to understanding MEMOA is to be able to identify the individual active ingredients and their weed control targets in a product and which herbicide groups the tank mix partners are included in. Although some products may indicate they have multiple modes of action in a product, sometimes marketing can be misleading. It may be that a product with multiple modes of action may include one active ingredient that works on broadleaves and a second active that works for grasses, which is not providing multiple modes of action on individual weed targets. Other factors such as rates and herbicide-resistant weed profiles need to be considered when determining if the tank mix includes effective products for the management needs.


“Recognizing the challenge of assessing and selecting the appropriate herbicide products and tank mix options for specific weed management targets and herbicide resistance risks, we are trying to find a way to support those decisions and make it easier for producers,” says Tidemann. “We have developed a prototype for one crop so far to test the model, and continue to build the database of information. There is a lot of database building required in this project before we can fully test the tool. We are using various crop protection guides, starting with Alberta’s Blue Book, for the main crops and herbicides to include in the model. By starting with one crop in the prototype and adding one component at a time, it is easier to fix any coding problems as we go along rather than trying to fix problems over the entire model. Our goal is to develop the prototype tool more fully and get it up and working properly. Then we want to work with farmers to test the prototype and use it to make sure it is helpful in implementing their herbicide management strategy. We want this to be a useful tool that farmers will keep using over the long-term.” 

A second tool also under development in this project is a Herbicide Resistance Risk Calculator. Tidemann is collaborating with researcher Andrew Kniss and his team from the University of Wyoming who developed the first calculator for their region. The goal is to develop and customize a Herbicide Resistance Risk Calculator specific to western Canadian crops and herbicides. This interactive tool would allow producers to select a weed, known resistance, a four year rotation of crops and the herbicides they will use in each of those crop rotation phases. Based on this input, the tool will provide information on herbicide cost, herbicide efficacy and herbicide resistance risk. The tool will provide information about the effectiveness of the herbicides and mixtures being used. Of note, the tool assumes producers are using full recommended rates for each herbicide used in tank mixes and sequential applications. Producers are encouraged to use full recommended rates, as cutting rates as part of a mixture will reduce the effectiveness for resistance management. 

Until the tools become available, growers should continue to focus on finding ways of implementing MEMOA and carefully consider the long-term implications of herbicides being applied within their cropping system or rotation.

“When developing herbicide management and tank mix plans for any system, it is important to understand what herbicide groups the active ingredients are in, and which active ingredients provide control of your target weeds,” emphasizes Tidemann. “A tank mix is not a useful tool unless it provides multiple modes of action. Just because you have two or three different products in a tank mix doesn’t necessarily mean you are effectively tank mixing, and you may be spending money that may not be giving you the benefit you were hoping for. The overall goal is to lower selection pressure for additional herbicide resistance cases and keep our herbicides a viable tool for as long as we can.

“We are developing these decision support tools to try to help simplify decisions for implementing MEMOA strategies. We expect the final version of the decision support tool to be a web browser based tool or app. Growers would use the tool while developing their cropping plans and herbicide management strategies early in the season. It is not a tool they would use on their cellphone in the field, as effective tank mixing requires planning ahead. We expect to be able to provide opportunities for growers to test the tools later in 2023, with the goal of having a tested prototype completed by the end of the project at the end of March 2024. This project has been an interesting one for me as it is much more of a tech or concept transfer of making research accessible as a tool that growers can easily use for decision-making on their farm rather than strictly research based.”


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