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Bugs May Resist New Crops Faster Than Expected
By Scott Kilman
08/05/1999
The Wall Street Journal
Page A4
(Copyright (c) 1999, Dow Jones & Company, Inc.)
University of Arizona scientists said some insects might be able to develop resistance to the biotechnology industry's new bug-proof cotton plants more quickly than expected.
The peer-reviewed laboratory study, which is being published in today's issue of the science magazine Nature, signals that some genetically modified plants might become obsolete sooner than their inventors had planned.
Biotechnology executives were quick to challenge the study, saying among other things that it didn't resemble actual field conditions.
But if follow-up field studies find similar results, the Environmental Protection Agency would likely have to change the rules that farmers must follow in order to plant the novel crops. The EPA rules are designed to prevent so-called "super bugs" from evolving.
"There are some real concerns that resistance can evolve," said Bruce E. Tabashnik, head of the Tucson-based University of Arizona's entomology department and an author of the study. "Some strategies might need to be changed."
U.S. farmers are tending about 3.5 million acres of bug-resistant cotton this year, which is equal to about one-fourth of the total U.S. cotton acreage. The farmers use seed containing a gene transplanted from a common soil micro-organism called Bacillus thuringiensis.
The Bt gene tells the plant how to make a toxin that specifically kills caterpillars, such as the pink bollworm, a big pest in Southwestern cotton fields and the subject of the University of Arizona study. The introduction of Bt plants three years ago has allowed cotton farmers to cut by millions of pounds their annual use of synthetic pesticides, which end up killing bugs indiscriminately, including those that are beneficial to the crop.
The University of Arizona study strengthens the hand of environmental groups that oppose the development of bug-proof plants. They worry that exposing bugs to the Bt toxin every day increases the chances that enough resistant strains would evolve to make the natural pesticide ineffective.
Bt-based sprays have been popular with vegetable growers for decades, because the toxin doesn't harm beneficial insects such as ladybugs and honeybees.
The EPA requires that farmers who plant Bt cotton and Bt corn set aside some of their fields as insect havens. The refuge is intended to guarantee that there are plenty of conventional insects around to mate with any that might develop Bt resistance. According to regulators, random mating reduces the odds that the next generation of bugs might inherit the Bt-resistant trait.
Bt-resistant bugs have yet to be found in actual U.S. corn and cotton fields. Indeed, in a bit of good news for the biotechnology industry, the University of Arizona study concluded that their laboratory-raised pink bollworms got their Bt-resistant abilities from a recessive trait. That means any progeny from a mating with a conventional pink bollworm won't express the trait.
The potential problem exposed by the University of Arizona study is that the mating cycle of its Bt-resistant bugs was out of synch with that of regular pink bollworms. That suggests any Bt-resistant bugs that develop in the wild might only be able to mate with each other, which could
trigger a population explosion of their kind.
Stephen Johnson, the EPA deputy administrator in charge of pesticides, said the agency will study the University of Arizona report to see whether it needs to take additional steps to regulate Bt crops. The EPA has approved nine Bt crops for planting in the U.S., including a bug-proof potato.
"This is a rapidly evolving science," said Mr. Johnson. "We will be constantly diligent."
Some cotton-insect scientists said yesterday that the refuge strategy is adequate to prevent Bt-resistant pink bollworms from developing. So many of those shortlived bugs are hatching at any time that there are always plenty of conventional bugs around for breeding purposes, they said.
Still, many scientists say it is only a matter of time before bugs in the wild develop some sort of resistance to the current stable of bug-proof crops; the debate is over the length of time it will take.
That is one reason crop- biotechnology companies such as Monsanto Co. are developing new insecticidal genes they can put into crops in order to stay ahead of bug evolution. The second generation of Monsanto's bug-proof plants might hit the market as early as 2001.