Fall armyworms in southern Florida survived a pesticide engineered into corn by Dow Chemical Co. (DOW) and DuPont Co., the second insect to show signs of resistance to genetically modified crops in the U.S., according to a study.
Fall armyworms ate the leaves of corn engineered to produce an insecticidal protein and lived, according to 2012 field trial data presented Nov. 13 at a conference in Knoxville, Tennessee. The protein is marketed by Dow and DuPont as Herculex.
"This is most likely field resistance," Fangneng Huang, an assistant professor at Louisiana State University in Baton Rouge, said at the annual meeting of the Entomological Society of America.
The study follows last year's discovery in Iowa that rootworms have developed resistance to Monsanto Co. (MON)'s corn. Concern that the insecticides are failing is prompting farmers to apply more chemicals, unwinding the primary environmental benefit of pest-fighting crops, Michael Gray, an entomologist at the University of Illinois in Urbana, said in a Nov. 14 presentation at the conference.
Fall armyworms, the caterpillar stage of a moth, got the name because infestations move between fields like a marching army, typically in autumn. The insect can survive U.S. winters only in southern Florida and Texas, limiting its range as a pest to the southeast.
Dow hasn't seen Huang's data and can't confirm his claims, Garry Hamlin, a spokesman for the Midland, Michigan-based company, said in an e-mail. A finding of armyworm resistance "would seem to have little agronomic significance for U.S. growers operating north of Tampa," he said.
DuPont's Pioneer seed unit sells "a minimal amount" of corn with the Cry1F protein in Florida and doesn't expect a business impact, Josh St. Peters, a spokesman for the Wilmington, Delaware-based company, said in an e-mail. A Dow study earlier this year found no indications of armyworm resistance, he said.
Armyworm isn't a primary target of the insecticide produced by the crop, the companies said separately.
The companies will work with the U.S. Environmental Protection Agency, which regulates pesticides, to determine the next steps. Dale Kemery, an EPA spokesman, had no immediate comment when reached by phone yesterday.
Fall armyworm resistance to the insecticide was first discovered in Puerto Rico in 2006, prompting Dow and DuPont to voluntarily stop selling the product on the island, according to the EPA's registration for the product.
DuPont's agriculture unit is its largest business, generating 24 percent of company sales last year, including $4.31 billion in corn seed revenue. Dow's agriculture unit, which doesn't break out seed sales, had $5.66 billion of revenue last year, according to data compiled by Bloomberg.
Also contributing to the armyworm study were scientists from the USDA, University of Florida, University of Minnesota and Louisiana State University.
Resistance to Monsanto's rootworm-killing protein is suspected in Iowa, Illinois, Minnesota and Nebraska, the EPA said last year. There's "mounting evidence" the engineered corn is losing its effectiveness in the Midwest, the agency said in August.
Syngenta AG (SYNN)'s Agrisure corn may have "cross-resistance" with Monsanto's insecticide, meaning the crop is vulnerable to the same rootworms that are no longer killed by Monsanto's toxin, according to other presentations at the conference this week.