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Senior Advisor

Corn rootworm resistance to Bt

ISU has found some corn rootworms that are resistant to one of the Bt strains.  It is in corn on corn in Northeast Iowa and there is a question of whether adequate refuge is being planted.  It's discussed in this Illinois paper.


Other Bt toxis are still effective. This story makes one think about good corn rootworm management.  Will we be back to insecticides?  I hope not.


 Corn rootworms in northeastern Iowa have become resistant to one of the Bt toxins commonly inserted in may corn hybrids. They are being controlled if the hybrid has a second toxin. Most of the resistance has come in fields of continuous corn, and in areas where refuge compliance is at a low level." 

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4 Replies
Frequent Contributor

Re: Corn rootworm resistance to Bt

"Refuge compliance is low"


Sometimes we are our own worst enemy!

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Re: Corn rootworm resistance to Bt

   Ya,  what do they expect.

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Senior Contributor

Re: Corn rootworm resistance to Bt

This is no different than the glyphosate resistance being created with weeds. Someday and probably sooner then later, it will be used mostly as a grass killer, tankmixed with a couple of other products. A few steps forward, few steps back...MikeM

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Re: Corn rootworm resistance to Bt

I've always planted the required refuge and like everyone else, bite my lip when combining it every year since there definitely is a yield drag, but I don't think there is any question that many farmers have not been honest with regards to the refuge.  I had one neighbor bragging to me last spring how he always depends on the neighbors to plant his refuge and that right in front of my 12-year old son.  It was a good lesson for my son as we talked about it later and what he was really saying.  Now one can certainly argue whether any refuge, no matter the size, is really enough to head off problems like these, but it's sad when we can't trust our neighbors to do the right thing.

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