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Bt toxin engineered into GM corn no longer works against pests, study finds

Bt toxin

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(NaturalNews) There's more trouble in GMO paradise as a popular genetically engineered trait bred into some strains of transgenic corn is reportedly losing its ability to ward off certain pests. Researchers from North Carolina State University (NCSU) and Clemson University have found that the crop pest corn earworm no longer responds to Bacillus thuringiensis (Bt) toxin, rendering the GM trait useless for this particular application, as was widely predicted.

Also known as Helicoverpa zea, corn earworm has long been known to attack not only corn but a variety of other food crops, including tomato, cotton, beans, alfalfa and tobacco. Once the pest gets hold of a crop, it eats the market product, in this case corn kernels, rendering the crop both unsaleable and unusable. Bt toxin, at least at first, was shown to be an effective deterrent for this invasive pest, but things have since changed.

Publishing their work in the journal Environmental Entomology, researchers from the two schools looked at multiple crop sites in both North and South Carolina over the course of two years, looking to see how Bt protein, which is converted into the actual toxin known as Cry1Ab, is working today against corn pests. The last time the effectiveness of Bt toxin had been evaluated in this way was in the 1990s when the GM trait first hit the market.

Compared to when it was first released, Cry1Ab now has "little or no effect" on the number or size of H. zea larvae compared to non-Bt corn. In other words. Bt corn is no longer an effective GMO for targeting corn earworms.

"There was a warning that zea could develop a resistance to this toxin," stated Dominic Reisig of NCSU, one of the paper's co-authors. "But no changes were made in how to manage Cry1Ab, and now it appears that zea has developed resistance."

Chemical companies can't just keep engineering new GMO toxins to replace failed older ones, warn scientists

While the authors admit that they can't say for sure that H. zea has developed resistance to Bt toxin, since their research was conducted in the field rather than in a laboratory, the evidence is suggestive that Cry1Ab toxin is no longer effective against this invasive pest. And the only logical explanation for this is that H. zea has already adapted to this shortsighted approach to pest management.

"Our focus was on determining if there were real-world effects, and there were," added Reisig. "This may also explain why zea - a significant cotton pest - is becoming less responsive to a related toxin used in GM cotton called Cry1Ac."

Adding to the argument is the fact that there's really no single defined way to identify resistance. Scientists have been observing a pattern of resistance developing in all sorts of GMO applications for many years now, including with the emergence of glyphosate-resistant weeds and "superbugs." The more pesticides that chemical companies inject into GM crops, the more pests seem to be figuring out ways to bypass them, scientists are observing.

"These findings are a reminder that we need to pay attention to potential clues about developing resistance," said Reisig, noting that field observations like his own "are screaming that changes are happening, but that this is largely ignored."

"We can't expect there to always be a new GM toxin available to replace the old one."

The full paper, entitled "Inhibition of Helicoverpa zea (Lepidoptera: Noctuidae) Growth by Transgenic Corn Expressing Bt Toxins and Development of Resistance to Cry1Ab," is available through Oxford University Press:

You can also help release the GMO stranglehold on agriculture by signing the following two petitions calling on Lowe's and Home Depot to stop carrying Monsanto's Roundup herbicide:

Home Depot:








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