Some scientists are expressing concern that a widely used variety of genetically modified corn plant, known as Bt corn, has grown vulnerable to the very pests it was designed to resist. Bt corn, which accounts for 65 percent of all U.S. corn acreage, was developed by Monsanto Co. and introduced in 2003. This biotech strain is created by incorporating a gene from a common soil bacterium into the plant so that it produces a toxin to ward off rootworms a pest that is particularly destructive to corn crops. As a result, farmers are able to reap larger harvests more effectively and with fewer costs.
Now, unfortunately, studies have found that these corn rootworms are developing resistance to Bt corn, especially in Iowa and some other Midwestern states. The cause of the resistance may be twofold: One is insufficient crop rotation, which involves planting other crops alternately with corn. Planting Bt corn every year makes it easier for pests to develop resistance. Unfortunately, farmers have become less consistent about practicing crop rotation, largely because it s more profitable for them to continually grow corn. Another probable cause of resistance is that growers have not planted an adequate amount of conventional corn within their Bt fields. Such tactics allow non-resistant pests to flourish and compete with the resistant ones, keeping the resistant population down. In 2003, 90 percent of farmers met the standard, as set by the Environmental Protection Agency, to dedicate 20 percent of their fields to non-Bt corn. Today, only about 70 to 80 percent adhere to that measure.
The EPA, however, seems to be admonishing Monsanto, instead of the farmers, for not adequately monitoring the suspected resistance. Such actions surprise ACSH s Dr. Gilbert Ross, who thought that the agency was more rigorous about enforcing their own mandates. I m surprised, he says, that more farms weren t shut down or severely chastised for neglecting to adhere to these scientifically grounded rules.
And adopting these measures is very important. As Gregory Jaffe, biotechnology director at the Center for Science and Public Policy, warns, This is a public good that should be protected for future generations and not squandered too quickly.
But there s still time for the Bt corn to be salvaged as a viable crop. ACSH s Dr. Ruth Kava notes, Certainly, farmers should be strongly encouraged to follow best practices in order to reduce the possibility of resistance. But on a positive note, there are several variants of Bt toxins that could be used against this pest.