Canada: European Corn Borer Bt Resistance Confirmed

European corn borer larva and damage. Photo: Bruce Potter

It was recently confirmed that European corn borer (ECB) has developed resistance to the Cry1F protein in Bt corn in Nova Scotia. More information on this issue can be found here: Canadian Corn Pest Coalition Mitigation Recommendations for European Corn Borer Resistance to Bt Corn (Cry1F) in the Maritimes. Thanks goes to Dr. Jocelyn Smith and Dr. Art Schaafsma at the University of Guelph Ridgetown Campus for their hard work at making the collections and running the tests to confirm resistance.

Until we know whether the resistant ECB population has spread beyond the Maritimes, we recommend that all corn growers across Canada keep an eye out of any ECB damage showing up on any Bt corn hybrids this year and consider implementing the mitigation strategies in the document above to help reduce the spread of the resistance. This especially applies to those regions that have shorter growing seasons with limited selection of Bt hybrids to choose from.

In addition, extension entomologists recommend that growers should not purchase or plant single-trait Bt hybrids for ECB. Hybrids containing only Cry1F (Herculex 1 and Herculex XTRA) or Cry1Ab (some Agrisure hybrids) should be avoided as the risk of resistance increases if only one trait is being used to control ECB. The Bt trait table has been modified to indicate the number of traits control each pest: Bt Corn Products/Traits Available in Canada – As of May 2019

Growers should also avoid planting stacked hybrids that contain only two Bt traits, if one of those traits is Cry1F. The confirmation of resistance to Cry1F results in these two trait hybrids becoming a single trait hybrid in those regions where Cry1F resistant ECB populations exist. If still planting these hybrids, use caution and scout for unexpected damage.

A structured refuge of 20% non-Bt corn within 400 metres of the Bt planting should accompany any hybrids that contain Cry1F and only one other Bt trait against ECB.

The following table indicates which traits control and do not control ECB. Growers should ensure that the hybrids they are planting includes at least two traits that control ECB.

Bt traits that control ECB Bt traits that do not control ECB
Cry1Ab Vip3A
Cry1A.105 Cry1F – in the Maritime Region
Cry2Ab2 mCry3A (only controls rootworm)
Cry1F – use with caution in regions outside of the Maritimes Cry34/Cry35Ab1 (only controls rootworm)

If you have any questions about ECB or Bt resistance, please contact your corn company agronomist or any of the provincial specialists listed below:

Province Contact Phone Email
Nova Scotia Angela Gourd (902) 956-0981 angela.gourd@novascotia.ca
New Brunswick Chris Maund (506) 453-3477 chris.maund@gnb.ca
PEI Sebastian Ibarra (902) 314-0388 sibarra@gov.pe.ca
Quebec Julian Saquez (450) 464-2715 ext. 249 julien.saguez@cerom.qc.ca
Quebec Tracey Baute (519) 360-7817 tracey.baute@ontario.ca
Manitoba
John Gavloski (204) 745-5668 john.gavloski@gov.mb.ca

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