Genetically Modified Corn May Not be Effective Against the Corn Earworm

It turns out that genetically modified corn may not protect against the corn earworm. Scientists have discovered that the earworm is developing resistance to the corn, which is consistent with predictions that were made almost 20 years ago that were largely ignored.

The genetically modified crop, in this case, is corn that produces a Bacillus thuringiensis (Bt) protein which, in turn produces a toxin called Cry1Ab. This GM corn was originally designed to combat a pest called the European corn borer (Ostrinia nubilalis) and went on the market in 1996.

In the late 1990s, researchers found that Cry1Ab was also affected against H. zea. However, they predicted enough of this species were surviving to develop a resistance to the protein. That's why, 15 years later, scientists wanted to see if resistance was actually occurring.

"We wanted to do an observational study in the field to see how, if at all, things have changed since the work done in the 90s-was there any indication that zea was becoming resistant," said Dominic Reisig, one of the researchers, in a news release.

The scientists found that now Cry1Ab now has little or no effect on the number of H. zea compared to non-Bt corn.

"There was a warning that zea could develop a resistance to this toxin," said Resig. "But no changes were made in how to manage Cry1Ab, and now it appears that zea has developed resistance."

Currently, the findings are of limited economic impact. Companies have already developed new and more effective Bt toxins to use against H. zea. With that said, the study is important; the methods reveal that resistance can be developed over time, which is especially important to note when creating genetically modified crops.

"These findings are a reminder that we need to pay attention to potential clues about developing resistance," said Reisig. "We can't expect there to always be a new GM toxin available to replace the old one."

The findings are published in the journal Environmental Entomology.

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