Genetically modified corn was created so that farmers planting it could minimize their use of pesticides. Since Monsanto’s Bt corn, which has been genetically modified to resist rootworm, was introduced in 2003, farmers have been using fewer pesticides. But recently, they have had to turn back to these again because the rootworms have, in under a decade, started to develop immunity to Bt corn.
In other words, not only are fields across the U.S. being sown with GMO corn. They are also, once again, being doused with chemicals.
“Thanks” to widespread planting of Bt corn, only 9 percent of the U.S. corn crop had to be treated with pesticides in 2010 in contrast to one-quarter of the corn crop in 2005, says Grist. But as the Wall Street Journal reports, sales of corn insecticide made by Syngenta more than doubled in 2012 as a result of “increased grower awareness” of rootworm resistance in the U.S.
The rootworms have developed resistance to seeds that have been genetically modified for one root worm trait; Monsanto says it will be phasing out that type of seed. Rootworms who develop resistance to one type of seed can certainly do the same for another, the Environmental Protection Agency points out.
That is, the “pest resistance” of genetically modified crops is by no means permanent. Indeed, it seems to be leading to the development of rootworms with all manner of new traits and with, in particular, immunity to more and more of the pesticides that we create to kill them.
We should not be surprised that this has happened. As Claire Thompson at Grist points out, some corporations, including American Vanguard, predicted that rootworms would develop such immunity to Bt corn and, accordingly, “bought a series of insecticide companies and technologies during the past decade.” American Vanguard is now watching its revenues from soil insecticide double.
Indeed, a new research study has shown that cockroaches evolve to lose their liking for things that taste sweet. As a result, a strain of cockroaches in Europe is now resistant to poison because the insects’ taste receptors have evolved so that sweet things taste bitter to them. These “mutant” cockroaches are simply “repulsed” by the taste of something sweet. Scientists who offered jam to the cockroaches say that their response was to behave “like a baby that rejects spinach.”
“The process of natural selection would strongly favor any chance genetic change that caused a cockroach to avoid the bait and therefore death,” as George Beccaloni, curator of cockroaches at the Natural History Museum, observes in the BBC. Cockroaches who taste sweet as bitter — and rats who have become resistant to the poison warfarin and rootworms who are immune to Bt corn — simply have a better likelihood of surviving and therefore reproducing; their descendants then replace those who lacked these changes.
One has no doubt Monsanto’s scientists are hard at work re-engineering GMOs like Bt corn so ringworms are no longer immune to them. It’s probably also reasonable to suspect that companies like Vanguard are making plans to have a good stock of insecticide companies in their holdings in the next seven or so years as, by that time, these chemicals wil again to be needed to fend off a new strain of super-immune ringworms.
Photo via Nicholas Kemp-Greenhood/Flickr