DvSnf7 dsRNA is an unusual insecticide. You don’t spray it on crops. Instead, you encode instructions for manufacturing it in the DNA of the crop itself. If a pesky western corn rootworm comes munching, the plant’s self-made DvSnf7 dsRNA disrupts a critical rootworm gene and kills the pest.
This last step is called RNA interference, or RNAi, and the Environmental Protection Agency last week approved the first insecticide relying on it. Just a few years ago, RNAi was the hot, new biotechnology generating both hype and controversy. But its first approval as an insecticide has been surprisingly low-key. The EPA’s decision attracted little attention from the press or even from environmental groups that reliably come out against new genetically modified crops.
The first product DvSnf7 dsRNA will show up in is SmartStax Pro, a line of genetically modified corn seeds made in collaboration between two agricultural giants, Monsanto and Dow. The RNAi part comes from Monsanto, which has its eye on a number of RNAi applications. Monsanto expects corn seed with RNAi to be on the market by the end of this decade.
For some corn farmers, this can’t come soon enough. The western corn rootworm is known as the “billion dollar pest” because of the damage it wreaks on cornfields. And it keeps becoming resistant to the toxins farmers throw against it. First it was spray-on pesticides; then it was corn genetically modified to make the Bt toxin, a technology also commercialized by Monsanto. “When I go out and I talk to farmers,” says Joseph Spencer, an entomologist at University of Illinois at Urbana-Champaign, “you talk about Bt resistance and invariably the moment will come where they say, ‘We’ll have the RNAi soon and that’ll take care it.’” To cover all the bases, SmartStax Pro will contain both Bt and DvSnf7 dsRNA.