Managing Herbicide Resistance in Cereals


Kochia is just one example of a weed with known herbicide-resistant biotypes.

When herbicides that once worked well stop working, an increase in the population of herbicide-resistant weed biotypes occurs as a result of selection pressure.

In many cases, herbicide-resistant biotypes in a weed species already exist in nature. Over time, these resistant biotypes survive herbicide applications, produce seeds and eventually predominate the population.

According to Bayer Cereal Expert Kevin Thorsness, “Anything that reduces the opportunity for an herbicide to perform at its maximum is going to play a role in developing resistance.” Therefore, growers should strive to keep their herbicides working effectively long-term by maximizing the efficacy of each herbicide application.

Strategies for Managing Herbicide Resistance

To maximize the efficacy of your herbicide program and mitigate the development of herbicide resistance, Thorsness recommends using the following five strategies:

  1. Identify weeds
    One of the most important steps to managing herbicide resistance is identifying the weeds that are present in your field and understanding if the weeds are resistant to the herbicide you plan to use. If that is the case, Thorsness advises adjusting your herbicide spray recommendations accordingly.
  1. Use multiple effective sites of action
    “To help manage herbicide resistance, it is important for growers to understand the different sites of action and what herbicide groups are effective on the weeds in their fields,” said Thorsness. “It is also important for growers to make sure they are using multiple effective sites of action on the same fields.”

    In fact, research from the University of Illinois demonstrated that growers who use an average of 2.5 effective sites of action per application are 83 times less likely to have herbicide-resistant weeds than those who use 1.5 effective sites of action, on average.1

    To easily manage a wide spectrum of weeds in cereal crops with multiple effective sites of action, Thorsness recommends using Huskie® herbicide (Groups 6 and 27) or Huskie® Complete herbicide (Groups 2, 6 and 27). 

    Powered by two sites of action, Huskie provides effective control of a wide spectrum of broadleaf weeds in winter wheat, spring wheat, barley and sorghum. With three sites of action in one formulation, Huskie Complete manages many grass and broadleaf weeds, including Groups 1- and 4-resistant weeds, in spring wheat, winter wheat and durum.
  1. Apply at the correct use rate for the weeds you are targeting
    “One of the ways herbicide resistance has developed over the course of time, is not using the labeled rates for products,” said Thorsness. To maximize herbicide efficacy and prevent the development of weed resistance, be sure to use the labeled rate for the weed species you are targeting.
  1. Target weeds when they are three inches or less
    Targeting weeds at the correct weed size according to label recommendations helps maximize the efficacy of the herbicide and ensure a greater number of weeds will be controlled. In most cases, Thorsness recommends targeting weeds when they are three inches tall or less. “If you’re spraying five- or six-inch weeds, those weeds are generally going to be more difficult to control than three-inch weeds,” said Thorsness.
  1. Use the correct nozzle type for proper coverage
    “If you’re using the wrong nozzle, you’re not going to get as good of coverage and you’re going to allow weeds to escape,” said Thorsness. Therefore, it is important to use the correct nozzle that delivers a droplet size that is recommended on the herbicide label to ensure proper coverage, which will help to effectively control weeds.

Overall, it is important to respond quickly to challenging weed populations. “If you start to see something happening in your field, you need to be proactive,” said Thorsness. “If there is a resistant weed species or biotype moving into your area and you see that weed in your fields, make sure you pull it and get it out of there. You need to strive for the best possible control you can achieve in every field.”

To learn more about Huskie or Huskie Complete, contact your local Bayer Cereal Expert.

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Huskie® Complete is a restricted use pesticide. Not all products are registered in all states and may be subject to use restrictions. The distribution, sale, or use of an unregistered pesticide is a violation of federal and/or state law and is strictly prohibited. Check with your local dealer or representative for the product registration status in your state. Bayer, Bayer Cross and Huskie® are registered trademarks of Bayer Group. For additional product information call toll-free 1-866-99-BAYER (1-866-992-2937) or visit our website at Bayer CropScience LP, 800 North Lindbergh Boulevard, St. Louis, MO 63167. ©2020 Bayer Group. All rights reserved.

Works Cited

  1. Henry, S. “Illinois: Tank Mixing Vs Herbicide Rotation To Stop Resistance?.” AgFax, 2015.
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