By Tracey Baute, OMAFRA Field Crop Entomologist.
Posted on Field Crop News.com
It was recently confirmed that European corn borer (ECB) had developed resistance to the Cry1F protein in Bt corn in Nova Scotia. More information on this issue can be found on the Corn Pest.ca website.
Thanks go 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 for 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 a 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.
Growers should ensure that the hybrids they are planting include at least two traits that control ECB.
Bt traits that control ECB are Cry1Ab, CryA.105, Cry2Ab2 and Cry1F (use with caution in regions outside of the Maritimes).
Bt traits that do not control ECB are Vip3A, Cry1F – in the Maritime Region, mCry3A (only controls rootworm) and 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 in the Field Crop News.com article.