Scientists Dismayed by Corn Rootworm Bt Resistance

They tell farmers, "I told you so:"

One of agricultural biotechnology’s great success stories may become a cautionary tale of how short-sighted mismanagement can squander the benefits of genetic modification.
After years of predicting it would happen — and after years of having their suggestions largely ignored by companies, farmers and regulators — scientists have documented the rapid evolution of corn rootworms that are resistant to Bt corn.
Until Bt corn was genetically altered to be poisonous to the pests, rootworms used to cause billions of dollars in damage to U.S. crops. Named for the pesticidal toxin-producing Bacillus thuringiensis gene it contains, Bt corn now accounts for three-quarters of the U.S. corn crop. The vulnerability of this corn could be disastrous for farmers and the environment.
“Unless management practices change, it’s only going to get worse,” said Aaron Gassmann, an Iowa State University entomologist and co-author of a March 17 Proceedings of the National Academy of Sciences study describing rootworm resistance. “There needs to be a fundamental change in how the technology is used.”
First planted in 1996, Bt corn quickly became hugely popular among U.S. farmers. Within a few years, populations of rootworms and corn borers, another common corn pest, had plummeted across the midwest. Yields rose and farmers reduced their use of conventional insecticides that cause more ecological damage than the Bt toxin.
By the turn of the millennium, however, scientists who study the evolution of insecticide resistance werewarning of imminent problems. Any rootworm that could survive Bt exposures would have a wide-open field in which to reproduce; unless the crop was carefully managed, resistance would quickly emerge.
Key to effective management, said the scientists, were refuges set aside and planted with non-Bt corn. Within these fields, rootworms would remain susceptible to the Bt toxin. By mating with any Bt-resistant worms that chanced to evolve in neighboring fields, they’d prevent resistance from building up in the gene pool.
But the scientists’ own recommendations — an advisory panel convened in 2002 by the EPA suggested that a full 50 percent of each corn farmer’s fields be devoted to these non-Bt refuges — were resisted by seed companies and eventually the EPA itself, which set voluntary refuge guidelines at between 5 and 20 percent. Many farmers didn’t even follow those recommendations......
There’s a lesson to be learned for future crop traits, Shields said. Rootworm resistance was expected from the outset, but the Bt seed industry, seeking to maximize short-term profits, ignored outside scientists. The next pest-fighting trait “will fall under the same pressure,” said Shields, “and the insect will win. Always bet on the insect if there is not a smart deployment of the trait.”

The kicker is that many of the expensive triple-stack and smart-stack hybrids have a hard time outperforming cheaper hybrids without the multiple traits.  When it comes to misusing products in a way that will engender resistance in targeted plants and animals, I don't think we can underestimate the foolishness of farmers (see Roundup resistant weeds).  I heard a farmer express complete shock last year about the Roundup-resistant pigweed (and marestail, and giant ragweed).  Hoocoodanode?  Maybe the weed scientist at Ohio State who had been warning farmers about weeds developing resistance for about a decade.  I remember the same farmer complaining about that scientist searching all over Ohio in order to find 3 or 4 plants that were Roundup-resistant.  He didn't seem to understand that if this guy could find Roundup-resistant weeds anywhere they would soon be everywhere, because they were going to continue to mutate, reproduce and spread.  And he's one of the more forward-thinking farmers I know.  I heard a number of farmers say that no weeds would be Roundup-resistant, because Roundup killed everything.

As far as the refuge goes, I was really tempted to go to a 50% or higher refuge, not so much because of the scientists' recommendations, but because the seed was $30 to $50 cheaper per bag, and seemed to out-yield the triple-stack seed.  I saw the Bt corn mixed in somewhat randomly in the field as a game of Russian Roulette for the insects, and they were eventually going to lose.  However, I didn't end up doing it, mainly because, like all the other farmers, I feared having a massive influx of insects decimate my field which was less-protected than my neighbor's field.  So you can put me in with the other foolish farmers in the "who's to blame" category.