(Reuters) — Armyworms are beginning to show increasing resistance to B.t. corn.
Fangneng Huang, an entomologist at Louisiana State University and lead researcher for a three-year study, called the evolution of insect resistance “ a great threat” to the long-term sustainability of genetic modification, which has become a highly valued tool for many U.S. farmers.
The study documented resistance by fall armyworms in the southeastern United States to the Cry1F protein found in many corn products developed Dow AgroSciences and DuPont to fight off the destructive pests.
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It is the latest evidence that insects are developing resistance to crops that have been genetically modified to kill them.
Like the 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, said Dominic Reisig, an entomologist at North Carolina State University.
Armyworms can be a problem for farmers in many states, but the resistant armyworms have been documented only in some areas of Florida and North Carolina.
Researchersy said farmers should plant more non-B.t. corn as a refuge and possibly increase the use of pesticides to control the resistance.
Officials with Dow said fall armyworm resistance is nothing new and not a significant problem.
DuPont said the company was trying to help farmers manage fall armyworms. The Cry1F protein still offers benefits, it added.
Researchers have also expressed concerns about B.t. resistance in western corn rootworm.
