Five steps to reduce your risk of herbicide resistance

Category: Grow Grain

Ready to make weed management part of your farm’s long-term strategy? Here are five proven steps to get you started.

Step 1: Tank mix – it’s critical

When you tank mix more than one mode of action that works on the same weed species, you dramatically reduce the risk of selecting herbicide resistance to either mode of action. 

Resistance to one herbicide mode of action is a rare event in a weed, and it takes years of selection pressure to develop a resistant population. But the chance of a weed having resistance to two effective modes of action is even more remote. That’s what makes tank mixing such an important strategy. On your farm, tank mix to aim for two different modes of action that target the same weed. 

Rotating herbicides may sound effective, but if you only use one product, you’re still selecting for resistance. Tank mixing two modes is more effective. 

Your pre-seed burndown is a great opportunity to use two modes of action. Let’s not spray glyphosate by itself – let’s add something in with our glyphosate so we have at least two modes of action working on our weeds at pre-seed.

Kochia concerns

If you mix a Group 2 product with glyphosate to control kochia, you’re really only spraying glyphosate on that kochia because it is Group 2 resistant. We need to diversify our options. 

For a pre-seed application on pulse crops and cereals, Heat® is a great option. It’s a Group 14, so for areas that don’t have glyphosate-resistant kochia yet, we get the activity of both glyphosate and the Group 14 on that weed. 

For a pre-seed application in canola, you can tank mix something like Pardner® (a Group 6 with bromoxynil) or Conquer™ (contains Group 6 bromoxynil and Group 14 carfentrazone) with your glyphosate to get two modes of action. 

Step 2: Diversify your crop rotations

A diverse crop rotation lets you introduce more modes of action in your herbicide rotation, so you can keep weeds off balance. Growing crops with different seeding dates, emergence times and herbicide options significantly lowers your risk of developing resistance compared to using a less diverse rotation.

Include crops that use herbicides you can’t spray in other years.  For example, add more cereals to your rotation so you can include Group 4 products, which you can’t use in oilseed or pulse crops. Pulse crops allow you to apply different Group 2 products than what you can spray in your cereals. 

Step 3: Use multiple modes in-crop

In-crop options for using multiple modes of action aren’t as abundant and take more planning.  So when you get to the cereal crop in your rotation, take full advantage of your many herbicide choices. 

Explore your options. Some co-packs and pre-mix cereal crop products already have more than one mode of action built right in. You can have a Group 4, 6 and 27 mode of action in one product. When you spray that on your cereal crop to control wild oats and broadleaf weeds, you know it’s also helping fight herbicide resistance. You can’t get this level of convenience and diversity in other crops, so put it to use when you can. 

Step 4: Don’t cut rates

This one is simple. When crop protection companies put in the work to register their products, they determine the minimum dose required for effective weed control. That’s the rate registered. When you cut rates, you end up with poor weed control, weed escapes and increased selection pressure for herbicide resistance. 

The small amount you save over the short-term can add up to big expenses in the mid- and long-term picture of your farm. Whether it’s yield loss or increased costs to deal with resistant weeds, cutting rates just isn’t worth it. 

Step 5: Test your weeds

If you’re starting to see escapes, or patches are getting bigger, those might be resistant weeds. Get them tested. Then you know what you’re working with. 

A wild oat isn’t just a wild oat anymore. Some are susceptible to all wild oat herbicides. Then there are Group 1, Group 2 and Group 8 resistant biotypes, plus various combinations. They may look the same, but they’re different. It’s almost like they’re different weeds, so they need to be treated differently. 

Your Cargill agronomist can help. Weed resistance management is but one of many services your industry-leading Cargill agronomic team provides. Cargill agronomists draw on the expertise of a national network, providing access to the most up-to-date information and advice to help your farm grow. 

Use our online form to book a free one-hour consultation with an agronomist in your area. You can also visit our Herbicide Resistance Resource Centre to learn more.

PARDNER® herbicide and LibertyLink are registered trademarks of Bayer. Heat is a registered trademark of BASF, CONQUER™ is a trademark of Nufarm Agriculture Inc.

Tags: Agronomy, Crop Protection, Herbicide, Weed Management, Herbicide Resistance

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