Manage Resistance Now


Bt crops have helped Canadian growers manage insect pests for more than two decades. Unfortunately, the development of resistance to these Bt corn hybrids is inevitable. However, growers can employ strategies to delay this and prolong the life of these important tools.



  • Scout your fields to know what pests are present and how much damage they have caused.
  • Correct identification and monitoring of corn pests are critical to making effective pest management decisions.
  • Know what pests should be controlled by the Bt corn being grown – not all corn pests are controlled by Bt traits.
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Rotate crops

  • Best option: do not plant corn in the same field in consecutive years, grow a different crop entirely in alternating years.
  • Alternative option: if planting corn consecutively, avoid planting Bt crops in the same field two years in a row. Use non-Bt varieties. This gives insects less exposure to Bt proteins, thereby slowing resistance developing.

Rotate traits for the target pest

  • Best option: plant Bt hybrids with multiple modes of action (MOAs) for the target pest whenever possible.
  • Alternative option: if a multiple-MOA product is not an option, rotate to a different Bt trait hybrid or use a non-Bt hybrid with insecticide.
  • Consult this Bt traits table for a complete list of traits available in Canada.
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  • Refuge planting is mandatory and involves planting part of each field (or adjacent field) with a non-Bt hybrid of the same crop. This allows some non-resistant insects to survive and mate with resistant insects, producing non-resistant offspring.

There are two types of refuge:

  • Integrated refuge: bag containing Bt seed mixed with non-Bt seed
  • Structured refuge: a specific area that you plant with a refuge hybrid alongside your Bt hybrid

Click here for more about Refuge Planting.

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  • Insecticides can be used in place of Bt crops to manage many pests. Before considering this, refer to Evaluating the Need for Insecticide Application.
  • Insects can also develop resistance to insecticides. For this reason, rotation of insecticide groups/MOAs is also critical. Refer to Insecticide Best Practices for more information about MOAs and application BMPs. Consider rotation of traited corn and conventional corn with use of insecticides.
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  • Keep accurate records of where traited and conventional corn has been planted and which hybrids were planted. This helps both you and your crop advisors compare the performance of your transgenic and refuge hybrids. It also helps to recognize a problem of suspicious feeding activity in the transgenic corn.
Test your knowledge
Steps to follow when you experience insect damage in your bt corn


Watch the Resistance Management School videos to learn more!

Episode 11

Kelly Turkington discusses: How do diseases become resistant to fungicides and what can we do about it?

Episode 10

Scouting and rotation key to maintaining effective pulse fungicides.

Episode 9

Albert Tenuta talks about the state of fungicide resistance in eastern Canada and recommends best management practices

Episode 8

In this episode we’re talking about how herbicide resistant weeds spread across Ontario and the continent.

Episode 7

How do you assess your risk of developing resistant weeds on your farm?

Episode 6

Manitoba farmer Gunther Jochum talks about their wild oat issues in this episode of the Resistance Management School.

Episode 5

Dr. Linda Hall discusses the state of herbicide resistance in Western Canada, and what growers can do about it.

Episode 4

Mike Cowbrough of OMAFRA joins us to discuss testing for herbicide resistance.

Episode 3

Lauren Benoit from the University of Guelph talks about how to manage multiple resistance in water hemp, discovered earlier this year in Ontario.

Episode 2

Kelvin Heppner talks to Rob Gulden about seeding rates in this episode of the Resistance Management School.

Episode 1

Dr. Peter Sikkema discusses the status of herbicide-resistant weeds in Ontario and provides growers with some best management practices.

More resistance management videos

Fungicide Resistance Management

Insecticide Resistance Management

CropLife International and IRAC explains the importance of mode of action in insect resistance management.