Did corn earworm develop resistance to Cry1Ab?

Did corn earworm develop resistance to Cry1Ab?

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From WATTAgNet:

An observational field study has found that a warning from scientists more than 15 years ago about organisms developing resistance to genetically engineered corn may have been correct.

Here are some key facts about the corn and the study that looked into the possible resistance:

  • Genetically engineered corn, which went on the market in 1996, produces a Bacillus thuringiensis (Bt) protein that produces a toxin called Cry1Ab, and was originally designed to resist the European corn borer.
  • In the late 1990s, scientists found that Cry1Ab also was effective against the corn earworm. But the scientists predicted that enough corn earworms were surviving that the species could develop resistance to Cry1Ab.
  • Now, more than 15 years later, preliminary testing shows that the corn earworm may have developed resistance.

“This finding is of limited economic impact at the moment,” said Dominic Reisig, an associate professor of entomology at North Carolina State and lead author of a paper describing the new study. “Because agriculture companies have already developed new, more effective Bt toxins for use against H. zea.

“But the study is important. The methods that are agreed upon to show resistance are somewhat arbitrary. The agreed upon metrics for demonstrating field fitness are laboratory studies with an agreed upon diagnostic dose of the toxin. I, and many others, feel that field observations are screaming that changes are happening, but that this is largely ignored. That was one reason for the study.”

Bt corn losing against corn earworm, Carolinas field study shows

A new study from North Carolina State University and Clemson University finds that the toxin in a widely used genetically modified crop is having little impact on corn earworm (Helicoverpa zea) – which is consistent with predictions made 20 years ago. “We wanted to do an observational study in …

Read more at Southeast Farm Press

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