Arizona has effectively eliminated the pink bollworm from the state's cotton crops, using a one-two punch of genetically modified cotton seed and release of sterile insects.
North of Tucson, where the cotton is high and the harvest is on, Arnold Burruel turned off his tractor for a few moments before sundown last week to talk about the milestone over his cell phone. He declared the effort a "success by committee" of growers, agricultural agents, research scientists and seed companies over the pink bollworm moth and its offspring caterpillars who once chomped their way through half of Arizona's cotton crop.
The moth was the target of a novel approach to pest eradication, which paired seed that had been genetically altered to produce a natural toxin called Bt, or Bacillus thuringiensis, with the release of sterile moths to guard against growth of an insect population resistant to the engineered seed.
That four-year assault reduced the pink bollworm population to essentially zero, says a research paper published this month in the journal Nature Biotechnology.
It's good news for farmers and beneficial to society at large, said University of Arizona entomologist Bruce Tabashnik. Growers have been able to virtually eliminate pesticide spraying on cotton crops in Arizona, he said.
The efficacy of Bt seed is nothing new, said Tabashnik, an author of the paper.
Worldwide, nearly 500 million acres are planted in Bt cotton and corn. It has proven effective in warding off pests, but some of Tabashnik's studies have raised concerns about the development of resistance by the insects it is supposed to kill.
No pesticide is 100 percent effective, and resistant insects can mate with each other to create a pest population that isn't killed by the Bt toxins.
That's why the EPA requires growers to set aside "refuge" plots, where genetically altered seed is not planted. That way, the small number of resistant bugs are more likely to mate with non-resistant ones.
That worked well in Arizona after the seed's introduction in 1996, and Tabashnik said he was at first skeptical when growers and agriculture agents proposed the idea of pairing the toxic seed with a sterile release program.
Theoretical studies convinced him it was possible, and those studies persuaded the EPA that it was safe to conduct the test.
So, over the past four years the U.S. Agriculture Department produced 8 billion sterile moths in a factory in Phoenix and released them in the cotton fields of Arizona.
That wasn't the end of the strategy. They also released clouds of female sex pheromones in non-Bt fields to confuse males seeking to mate.
It is impossible to say with any confidence what parts of the strategy worked, but it's clear that the combination resulted in a reduction of the pink bollworm population that is greater than 99 percent, said Tabashnik.
"I never dreamed that this would work as well as it has," he said. "I'm kind of a refuge promoter. When the growers first asked 'Can we eliminate refuges?' I said "If it ain't broke, don't fix it.'"
Cotton farmers are reaping the harvests of that success at a good time. Cotton prices as much as doubled in the past year, soaring to a record $1.52 a pound last week.
Rick Lavis, executive vice president of the Arizona Cotton Growers Association, said failed crops in Asia and lower prices for competing crops such as alfalfa induced growers to plant more cotton this year.
He estimates 200,000 acres were planted this year, up more than 40 percent over last year.
It's still a far cry from the 1970s when more than 600,000 acres of Arizona's fields were in cotton, but Lavis expects acreage to grow again next year. Controlling the pink bollworm is a big factor in that growth, Lavis said.
Burruel, whose family agricultural operation began 25 years ago, said he planted about 1,500 acres of cotton this year.
He regards the genetically engineered seed as "insurance" against crop losses.
"I'm paying $100,000 a year in tech fees, but I'm saving that much in the product I'm not using," he said.
Burruel said he has reduced his pesticide spraying by 90 percent, and he sleeps better.
"I don't lie awake at night listening to those bollworms chomping my cotton crop."
Agricultural organizations and major seed companies, Dow AgroSciences and Monsanto, supported the study. One of the co-authors, T.J. Dennehy, participated in the study as a UA entomologist. He is now employed by Monsanto, according to a declaration of competing interests filed by the authors.
ARIZONA COTTON
A better year:
Arizona's cotton production of all varieties is forecast as of Nov. 1 at 605,000 bales for 2010, 35 percent above 2009 production.
Value of 2009 production:
$138.76 million
Upland cotton.
$31.6 million
cotton seed.
$2.17 million
American-Pima cotton.
Source: National Agricultural Statistics Service
DID YOU KNOW
Cotton is one of the five "C's" - along with cattle, copper, climate and citrus - depicted on the state seal because they drove Arizona's economy at the time of statehood in 1912.
"I never dreamed
that this would work
as well as it has."
Bruce Tabashnik,
University of Arizona entomologist
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