European Corn Borer Resistance Confirmed to Cry1F

Bryan Jensen, Department of Entomology, Division of Extension

Perhaps this won’t come as a surprise, but field resistance has been confirmed in a European corn borer population to the Cry1F protein. However, you may be surprised to find out it was confirmed in Nova Scotia, a Canadian maritime province. Although you may not consider this area to be a corn growing powerhouse, you probably are wondering if this is an example of the “canary in the coal mine” like I am.

The only protein that was affected was the Cry1F which is common in many trait packages both as a pyramid and as a stand-alone above ground trait. For a better understanding of the trait packages please view the Handy Bt Trait Table.

What should this mean for Wisconsin? It means we need to be vigilant and actively looking for damage in hybrids using that protein. Either as a single trait or as a pyramid with other above ground proteins. If you find elevated damage, commonly referred to as Unexpected Damage (UXD,) over and above what you would expect in a RIB, report it to your sales representative. Don’t be bashful. Don’t dismiss it. Catching resistance at an early stage is beneficial to all.

Symptoms of first-generation ECB damage is window-paneing on corn leaves followed by either random or transverse holes in corn leaves. This happens as young larvae are feeding within the whorl prior to stalk tunneling. Second generation is a little more cryptic and can include entrance holes in the stalk commonly associated with frass, mid-rib feeding, kernel feeding, dropped ears, broken tassels and broken/lodged stalks.

Fortunately, many hybrids incorporate 2 or more above ground traits and only the Cry1F protein has been implicated at this point. Pyramids can be a good resistance manage tool, however, if resistance goes undetected in one of the proteins the other protein can mask resistance and this puts increased selection pressure on the viable protein.

On one hand the above ground traits have been viable for a long time. On the other hand, it is a matter of time before resistance was document. Keep an eye out for UXD and please report it if found.