Western corn rootworms have been showing resistance to GMO corn for several years. And now, scientists have confirmed that the insects have actually "evolved" a resistance to a type of genetically modified corn designed specifically to kill them. These genetically modified corn crops contain the Bt toxin—it's the bacteria Bacillus thuriniensis, and its function in the corn seed is to wreak havoc on the rootworm's digestive system, killing it.
BT corn has been used to reduce or eliminate the number of pesticide applications needed for farmers and the biotech industry has hailed it as environmentally friendly for its reduced need for pesticides. But the new findings may change all that.
According to research published in the recent issue of Proceedings of the National Academy of Sciences, the western corn rootworm is evolving fast to tolerate the Bt toxin. “Unless management practices change, it’s only going to get worse,” Iowa State University entomologist and study author Aaron Gassmann told Wired. “There needs to be a fundamental change in how the technology is used.”
Scientists and GMO skeptics have warned the biotech industry that resistant pests and "superweeds" would develop. The industry has responded to these issues with stronger pesticides and herbicides. For example, Dow USDA corn resistant to 2,4-D—half of the infamous Vietnam War defoliant known as "Agent Orange" is up for approval. But experts suggest pests and weeds will simply develop further immunity to the chemicals and that the only effective prevention are practices such as crop rotation.
"Crop rotation can suppress rootworm populations over time, reducing the threat posed by their new Bt resistance," reports Newsweek. "But Bt corn is still capable of warding off other pests, so farmers will likely keep planting it. Except now they’ll need to use pesticides to protect their crop from rootworms."
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