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Managing Group 9 resistance with pre-seed add-ins in your cereals

Read Time: 10 minutes

By Simon North February 22, 2018

The time to act is now


Whether you have observed it on your farm or not, we are seeing an increase in herbicide resistance across the globe and in Canada. What I see as most concerning is the increasing resistance to Group 9 chemistry, more commonly known as glyphosate products. But there are practices we can incorporate that can prevent resistance.

Glyphosate resistance is happening for the following reasons:

  • Limited or lack of crop rotation
  • Reduced or zero tillage operations
  • Continued use of glyphosate alone
  • Multiple applications in same season
  • Reduced rates of glyphosate

Glyphosate has been has been a great tool in crop production since 1976, and we need to preserve its effectiveness. Today in Canada there are more than 78 million acres treated with 14-plus brands of glyphosate. Thankfully, a cereal crop is a great crop in your rotation to  manage your group 9 herbicide resistance whereas in other crops the options are very limited.

How to preserve its effectiveness? Explore the use of tank mix partners from different herbicide groups when applying pre-seed in cereal crops. 

Benefits of a pre-seed burn-off

  • Reduces weed competition at an early stage when the crop is most vulnerable to weed competition.
  • Provides more options to control hard-to-kill weeds, such as perennials.
  • Can potentially reduce more costly in-crop herbicides.
  • Avoids the panic around getting in-crop spraying done if weather conditions prevent application.

Benefits of a pre-seed add-in

  • Resistance management, particularly against Group 9-resistant kochia.
  • Improved efficacy of hard-to-control weeds such as wild buckwheat, cleavers and narrow-leaved hawksbeard.
  • Residual activity. Some products have up to 30 days’ activity that glyphosate does not. Glyphosate alone would not control a number of spring annuals that germinate later.
  • Control of glyphosate-tolerant volunteer canola cannot be achieved by glyphosate alone.

Glyphosate selection pressure is greatest at low in-crop rates for many of the main weed species, so full rate of pre-seed glyphosate with an add-in is much more effective.


There are so many options now that can be mixed with any glyphosate to help with spring weed control. These now include:

  • PrePass™ Flex – Group 2
  • Express® Pro and Express® SG – Group 2
  • Paradigm™ – Group 2 and 4
  • Blackhawk® – Group 4 and 14
  • Goldwing® – Group 4 and 14

I recommend products that target specific problem weeds. For example, if volunteer canola is expected to be a problem, I would recommend going with PrePass Flex. If chickweed or dandelions are an issue, use a product such as Paradigm, which is now registered for pre-seed use as well as in-crop. The products from NuFarm, such as Blackhawk and Goldwing are great options to switch groups if you’re having problems with Group 2 broadleaved weed resistance.

To learn more about resistance management visit Bayer’s website or 


Always read and follow herbicide label directions. PrePass™ Flex and Paradigm™ are trademarks of Production Agriscience Canada Company, Dow AgroSciences and Pioneer affiliated companies or their respective owners. Express® Pro and Express® SG  are registered trademarks of FMC of Canada. Blackhawk®, Goldwing® and Fierce® are registered trademarks of Nufarm Ltd.

Simon North

Simon North

This British ex-pat specializes in Canadian in-crop chemistry, herbicides and canola production. Simon joined Cargill in 2014 after managing a large corporate farm in Saskatchewan. Prior to that, he worked for B.C.’s Minister of Agriculture.

“Canola needs the most attention; there is always something to do with it,” says Simon. “It’s the most expensive to grow, but we can also get the most output from it.”

Simon has been following canola breeding and innovation for many years. He first fell in love with agriculture when working on a farm in the U.K. following high school. There, and while completing his Bachelor of Science in Agriculture degree at Harper Adams University near Birmingham, he learned about oilseed rape production.

“It’s interesting to see how it’s evolved and what’s in the pipeline.“