AP News, November 2nd, 2007
A team of Arizona and Mexican researchers has engineered and tested a new version of a natural toxin to kill pink bollworms that develop a resistance to existing pest control methods.
Until the introduction 11 years ago of cotton genetically engineered to produce Bacillus thuringiensis toxins, pink bollworms were a huge threat to the $162 million Arizona cotton industry for 50 years, said Rick Lavis, executive vice president of the Arizona Cotton Growers Association.
Before that, farmers used heavy applications of pesticides to battle the pink bollworm pest, often with limited success.
"In 1990, we lost 40 (percent) to 50 percent of the crop to pink bollworm damage, and that was with efforts to control," said Jeff Silvertooth, head of the University of Arizona Soil, Water and Environmental Science Department.
This year, Lavis said an estimated 90-plus percent of the 181,000 acres of cotton planted in Arizona is the Bt toxin variety.
Although the existing Bt toxin — Cry1Ac — is now successful in controlling the pink bollworm threat, a team including UA researcher Bruce Tabashnik is planning ahead to handle pests that develop a resistance to the toxin.
Some other crop pests — the diamondback moth and cabbage looper worm — already have developed resistance to Bt, said Tabashnik, entomology professor and department head at UA.
Bt cotton is much "greener" than insecticides farmers used extensively to try to control pink bollworm.
Before Bt, pesticides were sprayed on cotton fields 10 to 15 times per year, Silvertooth said, adding that has dropped to 1.4 applications per field per year.
"This is special because it is so environmentally friendly," Tabashnik said. "They tend to be very safe and harmless to most living things other than certain species of insects."
The project included five researchers from the Universidad Nacional Autonoma de Mexico in Cuernavaca, Mexico, who developed the new toxin.
Tabashnik tested the new toxin on resistant pink bollworms that were developed with collaboration of Arizona cotton growers and researchers from the U.S. Department of Agriculture and UA.
In addition to Bt cotton, efforts to eradicate the pink bollworm threat includes introducing sterilized insects to cotton fields to reduce the number of offspring.
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Information from: Tucson Citizen, http://www.tucsoncitizen.com
