In 2018, our entomologist colleagues confirmed unexpected damage to Cry1F corn by European corn borer (ECB) in a few corn fields in Nova Scotia, Canada. Corn in these fields were single-traited, i.e. they only expressed the Cry1F toxin. There is no indication that any of the other above-ground traits were compromised. (Note: for a list of Bt traits in hybrids see the Bt trait table at https://lubbock.tamu.edu/files/2018/11/BtTraitTableNov2018.pdf). Monitoring will expand this year to see if these ECBs spread outside of Nova Scotia.
These observations in Nova Scotia should remind us that insects continuously adapt to control tools, and that good insect resistance management (IRM) practices are necessary to prevent resistance. While it is not entirely clear what factors led to unexpected damage in this case, they likely involved continuous use of a single trait (as opposed to multiple/pyramided traits), a small isolated population, and a lack of refuge compliance. The good news is that all of the other above-ground traits still work well against ECB. Any hybrids that contain Cry1F with an additional above-ground trait should still control ECB. And in Ohio, we have not seen any cases of unexpected damage by ECB on any traited corn. Nonetheless, we should continue to remember and use IRM and scouting so that these traits remain effective against this important pest.
For more information on the ECB resistance story in Nova Scotia, please see: http://fieldcropnews.com/2019/05/european-corn-borer-resistance-to-bt-corn-found-in-canada/