Volunteer corn threatens Bt hybrids
Volunteer corn is not an unusual problem to find in a typical soybean field. What is unusual is that it could threaten the effectiveness of Bt corn hybrids. In an Ag Professional article from earlier this year, Purdue University entomologist, Dr. Christian Krupke, said, "Corn hybrids containing insect-resistance genes could become more susceptible to corn rootworms unless growers keep soybean fields free of volunteer corn and continue planting refuge acres."
What concerns researchers are the insects that feed on volunteer corn with the Bt gene, exposing them to the toxin at less-than-toxic levels, contributing to increased resistance pressure. "We've looked at the relative sizes of rootworm beetles coming out of the transgenic and refuge corn and found some large females coming out of the transgenic blocks," Krupke said. "That is important because large females tend to lay more eggs and are preferred by the male beetles because they lay more eggs."
A January 2008 Ag Answers article said that volunteer corn can usually be controlled with herbicides. It becomes more difficult when glyphosate-tolerant (GT) volunteer corn pops up in fields planted to GT soybeans. Herbicides other than glyphosate need to be used for control. Plus, it's a good resistance management strategy.
Syngenta recommends using a pre-emergence residual herbicide on corn and soybean fields, and following 2-1-2, or two applications of glyphosate in one field over two years. A common thread among glyphosate-resistant weeds is that they have most often developed in fields continuously planted to GT soybeans and treated with solely glyphosate. With the increase in acres planted to GT corn hybrids, volunteer GT corn is becoming more common. For control of volunteer corn, Syngenta recommends Fusilade®. Or visit the Resistance Management Solutions Module to help find the herbicide program right for your field.
Are you struggling with volunteer corn? What management practices are you using? Have you seen issues with corn borers developing resistance?
Learn more about Fusilade and how it can help control volunteer corn.
Fusilade® is a trademark of a Syngenta Group Company.
Volunteer corn in a soybean field.