Another Bt Resistance Occurrence – European Corn Borer

Dr. Jocelyn Smith and Art Schaafsma at the Ridgetown campus of the University of Guelph recently reported a new and unexpected development in the resistance to Bt saga – this time it happened all the way out in the Maritime Corn Belt (MCB), in Nova Scotia, a province in Eastern Canada. Yes, they grow corn there! At under 30,000 acres annually, their production is not much of the grand total. But this story is worth following because it features an old, familiar target of the first-ever Bt corn commercialization, the European corn borer. Tracey Baute’s, University of Guelph Field Crops Entomologist, original newsletter article can be found HERE.

The insect toxin in question is Cry1F, which regular readers will remember is the same toxin that was once labeled for effective control of western bean cutworm, only to succumb to resistance in the US and Canada in the last several years.

What this means is that Cry1F expressing hybrids, should be monitored carefully for ECB damage in Indiana as well – if it can happen in Nova Scotia there is no reason that Hoosier corn borers cannot also adapt to this toxin. Complacency is the enemy in many aspects of agriculture, and Bt crops are no exception – periodic scouting is the only way we find these resistance stories in a timely manner, so that we can get the word out and try to contain resistant populations.

The good news is that some of the other Cry toxins targeting this pest are still efficacious, by all accounts. This includes Cry1Ab, Cry1A.105 and Cry2Ab2. If you are not familiar with these, and what hybrids contain which traits, you are not alone. As always, consult the Bt trait table (LINK HERE) when in doubt. We have been stacking multiple traits in each hybrid for years, and that trend should and will continue – because we are generally not equipped with high-dose traits for insect control, and this leads to resistance after continuous exposure.

That raises questions about the location of this resistance event – a geographically isolated part of Eastern Canada – and what we can learn about how resistance develops with respect to selection pressure, moth movement and gene flow. The hope is that this is an isolated event and can be contained with management approaches that limit subsequent exposure of ECB to Cry1F in those areas, while emphasizing higher dose Cry toxin deployment.

Stay tuned, there is likely more to come on this story in future issues!

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