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Angie Peltier

Angie Peltier
Former Extension Educator, Commercial Agriculture

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Hill and Furrow

Current topics about crop production in Western Illinois, including field crops research at the NWIARDC in Monmouth.
Figure. Large volunteer corn in Warren County, IL, June 2012.

Volunteer corn may contribute to development of Bt resistance in pest populations

In addition to potentially robbing crop yields, volunteer corn, or corn that grows on its own, rather than being deliberately planted, may increase the risk of Bt resistance developing more rapidly in target insect populations (Figure). Bt trait technology has been deployed by many seed corn companies. Bacillus thuringiensis, a bacterium, naturally produces proteins that create holes in the midgut of Lepidoptera (moth) insect larvae, killing them. Bt hybrids express one or more of the toxin genes from this bacterium in corn plants.

In a 2009 Agronomy Journal article, Krupke et al. describe that they observed Western corn rootworm larvae (WCR) feeding on volunteer plants expressing the Cry3Bb1 Bt protein at levels similar to Bt negative volunteer plants. They discuss that because the soil around these volunteer corn plants has not been amended with the nitrogen needed for protein synthesis as deliberately planted corn would be, volunteer plants likely express lower than target levels of the Bt toxin protein. They also speculate that suboptimal levels of the toxin protein may accelerate the development of pesticide-resistant insect populations.

In a 2011 article, Gassmann et al. confirm populations of WCR that developed field-resistance to the Cry3Bb1 Bt protein in Iowa. WCR feeding damage on corn expressing the Cry3Bb1 has also been observed throughout Illinois. It is not known whether volunteer Bt corn was directly responsible for these resistant populations and only time will tell whether WCR populations will develop resistance to other Bt traits. Carefully following seed label directions by planting non-Bt refuges and rotating Bt traits will help to preserve these valuable tools. Controlling volunteer Bt corn will also help to minimize risks associated with exposing the WCR to suboptimal concentrations of Bt proteins.


Gassmann AJ, Petzold-Maxwell JL, Keweshan RS, Dunbar MW (2011) Field-Evolved Resistance to Bt Maize by Western Corn Rootworm. PLoS ONE 6(7):e22629. doi:10.1371/journal.pone.0022629

Krupke, C., Marquardt, P., Johnson, W., Weller, S., and Conley, S.P. 2009. Volunteer corn presents new challenges for insect resistance management. Agronomy Journal. 101:797-199.

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