|
They point to two factors: farmers who have abandoned crop rotation and others have neglected to plant non-Bt corn within Bt fields or in surrounding fields as a way to create a "refuge" for non-resistant rootworms in the hope they will mate with resistant rootworms and dilute their genes. Experts worry that the actions of a few farmers could jeopardize an innovation that has significantly reduced pesticide use and saved growers billions of dollars in lost yields and chemical-control costs. "This is a public good that should be protected for future generations and not squandered too quickly," said Gregory Jaffe, biotechnology director at the Center for Science and Public Policy. Iowa State University entomologist Aaron Gassmann published research in July concluding that resistance had arisen among rootworms he collected in four Iowa fields. Those fields had been planted for three to six straight years with Bt corn
-- a practice that ensured any resistant rootworms could lay their eggs in an area that would offer plenty of food for the next generation. For now, the rootworm resistance in Iowa appears isolated, but Gassmann said that could change if farmers don't quickly take action. For one, the rootworm larvae grow into adult beetles that can fly, meaning resistant beetles could easily spread to new areas. "I think this provides an important early warning," Gassmann said. Besides rotating crops, farmers can also fight resistance by switching between Bt corn varieties, which produce different toxins, or planting newer varieties with multiple toxins. They can also treat damaged fields with insecticides to kill any resistant rootworms
-- or employ a combination of all those approaches. The EPA requires growers to devote 20 percent of their fields to non-Bt corn. After the crop was released in 2003, nine out of 10 farmers met that standard. Now it's only seven or eight, Jaffe said. Seed companies are supposed to cut off farmers with a record of violating the planting rules, which are specified in seed-purchasing contracts. To improve compliance, companies are now introducing blends that have ordinary seed premixed with Bt seed. Brian Schaumburg, who farms 1,400 acres near the north-central Illinois town of Chenoa, plants as much Bt corn as he can every spring. But Schaumburg said he shifts his planting strategies every year -- varying which Bt corn hybrids he plants and using pesticides when needed
-- to reduce the chances rootworm resistance might emerge in his fields. Schaumburg said he always plants the required refuge fields and believes very few farmers defy the rule. Those who do put the valuable crop at risk, he said. "If we don't do it right, we could lose these good tools," Schaumberg said. If rootworms do become resistant to Bt corn, it "could become the most economically damaging example of insect resistance to a genetically modified crop in the U.S.," said Bruce Tabashnik, an entomologist at the University of Arizona. "It's a pest of great economic significance
-- a billion-dollar pest."
[Associated
Press;
Copyright 2011 The Associated
Press. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
News | Sports | Business | Rural Review | Teaching & Learning | Home and Family | Tourism | Obituaries
Community |
Perspectives
|
Law & Courts |
Leisure Time
|
Spiritual Life |
Health & Fitness |
Teen Scene
Calendar
|
Letters to the Editor