Released: November 16, 2001

Re-Approval of Bt Corn Good News, Scientist Says

GARDEN CITY, Kan. – Word out of Washington last month that the Environmental Protection Agency had approved the use of Bt corn for another seven years is good news for farmers, a Kansas State University scientist said.

"The economics of Bt corn have made it very popular in our area," said K-State Research and Extension entomologist Phil Sloderbeck. "This maintains an option in a grower’s arsenal. It’s a way to help the grower reduce losses from corn borers."

Bt corn has been genetically modified with Bacillus thuringiensis [Bt], a naturally-occurring soil bacterium that produces a protein toxic to certain insects. Sprays containing this bacterium have been used for years to control various caterpillars, Sloderbeck said. They have been shown to be very specific in their range of activity. While they are able to kill certain insects by disrupting their feeding activity, they pose little hazard to humans and other organisms. Incorporating the bacterium into corn plants enables them to produce the same toxin and defend against certain corn pests.

The Bt corn has been particularly helpful in Kansas by lessening problems with the Southwestern corn borer.

"The use of Bt corn has curbed losses from the southwestern corn borer, no question – without control, [yield] losses can be significant," Sloderbeck said.

Research at K-State in 1997-98 in south central and southwest Kansas showed significant differences in the yield of Bt corn versus non-Bt corn. The total yield of the Bt corn [YieldGard brand] in fields that had not been sprayed with insecticide was 183 bushels per acre, compared with unsprayed fields of non-Bt that yielded 163 bushels per acre. Bt corn fields sprayed with an insecticide yielded 190 bushels per acre versus sprayed fields of non-Bt corn that yielded 175 bushels an acre.

In the study, even with the higher price of Bt corn, the significant differences in yields resulted in higher returns for the Bt corn than the non-Bt corn. The one exception was in the sprayed Bt corn. The small increase in yield gained from spraying Bt corn [190 bushels per acre] versus not spraying Bt corn [183 bushels/acre] was offset by the cost of spraying, the research showed. In that case, there was a small loss in returns for spraying the Bt corn.

"Bt corn has been evaluated thoroughly by EPA, and we are confident that it does not pose risks to human health or to the environment," said EPA assistant administrator Stephen Johnson in a statement announcing the seven-year re-approval.

The news came after a nearly two-year review, where the agency paid particular attention to potential risks to Monarch butterflies. "The scientific evidence demonstrates that Bt corn does not impact Monarch butterfly populations," the EPA said.

The EPA also has increased environmental and compliance monitoring requirements, including requesting additional data on the persistence of active protein in soil, field studies on non-target insects, and continued studies of Monarch butterfly populations and birds.

The research continues, Sloderbeck said, noting that K-State scientists are studying how new Bt "events" affect other insect species, including the corn root worm.

"These newer events, which are based on different selections of Bt toxins, are showing great promise in controlling many of the corn pests common in our area," he said.

For more information about Bt corn in Kansas, interested persons can visit http://www.oznet.ksu.edu/swareaoffice/entomology/latest.htm. 

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Mary Lou Peter, Communications Specialist
mlpeter@oznet.ksu.edu
K-State Research& Extension News