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Armyworm presence documented in Fla., NC

Crop-devouring armyworms are showing increasing resistance in some U.S. farm fields to a popular type of genetically modified crop that should kill them, scientists say.

Armyworms
A fall armyworm larva is pictured in Hyde County, North Carolina in this May 2014 handout photograph. Crop-devouring armyworms are showing increasing resistance in some U.S. farm fields to a popular type of genetically modified crop that should kill them, scientists said November 17, 2014. (Reuters/Dominic Ressig)

Crop-devouring armyworms are showing increasing resistance in some U.S. farm fields to a popular type of genetically modified crop that should kill them, scientists say.

The evolution of insect resistance "is a great threat" long-term to the sustainability of the GMO crop biotechnology that has become a highly valued tool for many U.S. farmers, according to Fangneng Huang, an entomologist at Louisiana State University and lead researcher for a three-year study.

The study was published on Nov. 17 in the PLOS One online journal ( www.plosone.org ) for peer-reviewed research, after being presented at the Entomological Society of America annual meeting in Portland, Ore.

The research documents resistance by fall armyworms in the southeast U.S. to the Cry1F protein found in many corn products developed by Dow AgroSciences and DuPont to fight off the destructive pests.

It is the latest evidence in recent years showing insects are developing resistance to crops that have been genetically modified to kill them.

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'Super bugs'

Like "super weeds" that have developed resistance to glyphosate-based herbicide and make it harder for farmers to keep fields from being overrun with weeds, the armyworms are starting to devour corn crops that should repel them, says Dominic Reisig, an entomologist at North Carolina State University.

Armyworms can be a problem for farmers in many U.S. states, but the resistant armyworms have been documented only in some areas of Florida and North Carolina. The range of these resistant armyworms is unknown, researchers say.

They say farmers should plant more nonGMO corn as a refuge and possibly increase the use of pesticides to control the resistance.

The GMO corn at issue contains Bacillus thuringiensis (Bt) genes. Bt corn, popular with farmers throughout the Americas, has been on the market roughly 18 years. Newer types of Bt corn with multiple modes of action are still showing effectiveness, Huang says.

"We don't know how long they can last," he says.

Officials with Dow say fall armyworm resistance is nothing new and not a significant problem. DuPont says the company was trying to help farmers manage fall armyworms and says the Cry1F protein still offers benefits.

Researchers have also expressed concerns about Bt resistance in western corn rootworm.

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The study was conducted by researchers from LSU, North Carolina State University, the University of Florida, the U.S. Department of Agriculture, the University of Minnesota and the University of Georgia.

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