By Dan Charles
Some of the most popular products of biotechnology — corn and cotton plants that have been genetically modified to fend off insects — are no longer offering the same protection from those bugs. Scientists say that the problem results from farmers overusing the crops, and are pushing for new regulations.
These crops were the original genetically modified organisms, or GMOs. They weren't the first ones invented, but they were the first to be widely embraced by farmers, starting in the late 1990s.
They got their bug-resistant features from a kind of bacteria that lives in the soil, called Bacillus thuringiensis, or Bt, which is poisonous to the larval stage of some major insect pests, including the corn rootworm and cotton bollworm. Scientists inserted some of these bacterial genes into corn and cotton, and the plants themselves produced these insect-killing proteins.
Bt crops brought a two-fold benefit: Cotton and corn farmers didn't need to use so many chemicals to control the bollworm and related pests after they were released, starting in 1996. "Our insecticide sprays just plummeted, and there were guys who wouldn't have to treat at all," says David Kerns, an entomologist at Texas A&M University, speaking of cotton farmers.
This was also good news for the environment. The Bt proteins are toxic to a relatively small number of insects, and they're practically harmless to people and other animals. Unlike the insecticides that they replaced, they were not killing significant numbers of pollinators like bees and butterflies, or beneficial insects that prey on pests and help to keep them under control.
Farmers like Jonathan Evans in North Carolina liked Bt cotton because it made farming easier. "It's always better for the plant to protect itself, than for us to have to go out and spray for the worm," he says. "You can tend a lot more acres, with a lot less equipment."
Now all of those benefits are increasingly at risk. Bt crops are losing their power. New strains of bollworms, rootworms, and other pests have emerged that are able to feed on Bt plants without dying. David Kerns says some farmers are pretty angry about it. "There are words I can't use," he says, "but they want to know what the heck they're doing, paying for a technology and then they're still having to spray."
The current situation is complicated by the fact that biotech companies have deployed close to a dozen slightly different Bt genes, targeting a variety of insects. In many cases, the bugs have evolved resistance to some Bt proteins, but not others, and the prevalence of Bt-resistant insects varies from place to place. "The impact can be patchy, but when it's there, it's big," says Julie Peterson, an entomologist at the University of Nebraska. "If you're the farmer who ends up with all of their corn laying down on the ground because the roots have been completely fed on by rootworm beetles, that's a huge impact to you."
Scientists have long warned about this risk. They've been engaged in a long-running argument with the companies selling Bt crops, such as Monsanto, which has been acquired by Bayer.
The EPA adopted this strategy, but independent scientists and biotech companies have disagreed over the years about how big these refuges need to be. In the case of some Bt crops, such as corn hybrids with genes targeting the corn rootworm, scientists have urged the EPA to require that farmers to devote at least half of their fields to non-Bt corn. The companies balked at that, since it would have limited sales of their products. They convinced the EPA that such large refuges weren't necessary.Click here to see more...
Even before Monsanto started selling the first Bt crops, independent scientists pushed the Environmental Protection Agency to limit the amount of land that farmers could devote to Bt crops. If these crops were planted everywhere, the scientists argued, it would create a situation in which, if a few rare insects happened to be genetically capable of surviving Bt proteins, they would be the sole survivors, quickly mate with each other, and produce a new strain of resistant insects. Biologists call this "selection pressure."
The solution, they said, was a requirement that farmers devote some of their land to non-Bt crops. This would allow plenty of non-resistant insects to survive, and make it less likely that the rare resistant insects would mate with each other.