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Bt Corn Good for Growers and Consumers

30.oct.01, Krista Thomas and Douglas Powell, Commentary from the Food Safety Network

30.oct.01, Krista Thomas and Douglas Powell, Commentary from the Food Safety Network
Two years of review came to an end recently when the U.S. Environmental Protection Agency (EPA) approved the use of genetically engineered Bt corn varieties for another seven years.
The news has been received quietly, unlike the furor that accompanied claims of harm to the Monarch butterfly or of a human allergen in the Starlink variety. But that is normal in media cycles, where the hypothetical is infinitely more interesting than daily grind of producing food that consumers may actually be interested in purchasing. Bt corn was among the first genetically engineered crops to be grown in North America, and it has been the subject of much scrutiny and controversy. A media flurry and an environmentalist uprising was sparked by a 1999 report that Bt corn pollen could harm Monarch butterflies as well as the corn pests the Bt gene was meant to target. Less publicized has been the continuing research designed to see if this could happen outside of the laboratory. In October 2001 results of field studies conducted over two years by researchers in Canada and several US states were published ( Though the issue had dropped off the public's radar, the scientific and regulatory community was all ears. Although there were some variations depending on the variety of Bt corn being grown, the overall result was clear: there are lots of risks to Monarch butterflies and Bt corn is near the bottom of that risk list.
The EPA's registration action document ( explained their decision to reregister Bt corn and elaborated on its benefits. Among the conclusions was that Bt corn can be safer to eat, can require less pesticides and can save growers money by yielding more, compared to conventional corn varieties.
The EPA estimated the annual financial benefits to American growers due to higher yields from planting insect-resistant Bt corn was as high as $220
million when insect pressure was high, and even $40 million in years of low insect pressure. After all, regardless of genetic engineering and whatever other high- and low-tech tools may be available, weather remains the biggest factor that influences a crop's outcome.
Bt corn was developed mainly as a means of controlling European corn borer, the most damaging insect pest of corn throughout North America. Severe corn borer infestations can reduce corn yields by ten percent or more. Entomologists estimate that losses resulting from ECB damage and control costs exceed $1 billion each year.
Conservative estimates place the value of Bt corn at $7-10 million annually in improved corn yields in Ontario in 1998, when about 20 percent of the
crop was planted to Bt varieties. Approximately 40% of the field corn acreage in Ontario was planted to Bt corn in 2001, according to the Ontario
Corn Producersí Association (OCPA).
But the benefits aren't just for farmers.
Mycotoxins are carcinogenic chemicals that are made by a fungal disease of corn called fusarium. The disease gets inside the kernels when corn pests create entry wounds. Since Bt corn is resistant to corn borer damage, the result is a healthier plant with less fusarium and fewer mycotoxins, up to 90 per cent less in some Bt corn varieties.
The FDA has new proposed new guidelines for acceptable mycotoxin levels in corn. If these guidelines became action levels, 160 million bushels of corn could be rejected at market every year. If Bt was instead grown, the savings would be several million dollars.
Lower mycotoxin levels aren't the only benefit Bt corn offers to consumers.
Bt varieties of sweet corn -- the corn on the cob cherished by many consumers for the fresh market are now available. Typically, sweet corn is more heavily treated with pesticides than other corn used for processing or animal feeds. The EPA estimates the upper limit of financial saving to growers using Bt corn at $45/acre from reduced pesticide treatments. Because Bt sweet corn had not been widely adopted at the time of the writing of the EPA's decision document, they could only predict the future benefits to human health and the environment, such as lower mycotoxin levels, and reduced use of acutely toxic organophosphate and pyrethroid pesticides. And the impact on non-target insects such as the Monarch butterfly? Field corn in Ontario is rarely sprayed to control corn borers; growers suffer lower yields instead. But sweet corn, whether for processing -- canned and frozen -- or the fresh market is sprayed to provide a product that consumers are interested in buying. Those sprays decimate all insects, including Monarch butterflies. The environmental benefits of Bt sweet corn have been well documented, and consumers are more than interested in this genetically engineered product.
A farm market in Hillsburgh, Ontario has been selling clearly labeled genetically engineered (GE) sweet corn alongside its conventional counterpart for two years. Consumers prefer the GE by a 2:1 margin. But it's not news. The re-registration of Bt corn varieties is, however, typical of agriculture: no magic bullets, but a series of small, incremental improvements that in the end produce a safe and increasingly sustainable food supply.
Krista Thomas is a research assistant and Douglas Powell is scientific director with the Food Safety Network at the University of Guelph.