COLLEGE STATION — Bt cotton may not have been a cure-all for insects in its debut year, but a Texas Agricultural Experiment Station entomologist said that farmers expectations also may have been too high.
The genetically-engineered cotton, otherwise known as Bt cotton, was promised to reduce insecticide use by more than 75 percent. It was grown commercially in Texas for the first time during the 1996 season, however, under certain conditions it did not work as well as had been expected, said Dr. John Benedict of Corpus Christi. Benedict was one of the guest speakers at the annual entomology conference held recently at Texas A&M University.
Bt cotton is modified to contain the genes that produce an insecticidal protein from the bacterium called Bacillus thuringiensis, Benedict said. The toxin is produced by the plant and the gene working together.
In studies conducted statewide in 1996 by the Experiment Station, Benedict found that Bt cotton still controlled 80 percent to 90 percent of the bollworms.
“It just wasn’t enough to make the growers happy,” he said. “They had an expectation, based on marketing, that there wouldn’t be any damage.”
There were several factors that limited the effectiveness of the biotech cotton, he said.
“The Bt has to be expressed in the plant through the genetics controlling that expression,” Benedict said, “and apparently it’s much better expressed in the younger plant than it is as the plant matures.”
Additionally, a dramatic increase in corn acreage and therefore corn earworms (alias cotton bollworms) — caused by higher-than- normal prices for that crop — brought on a greater population of insects.
The heavier infestation of bollworms during the 1996 growing season overwhelmed even the most resistant cotton, Benedict said.
Growers didn’t expect the higher numbers of worms and didn’t always scout carefully enough. Their crop was damaged before they knew it, he said.
Benedict hopes farmers don’t give up on Bt cotton because of one bad year. Scouting to catch infestations early in the growing season will help farmers better reap the benefits of Bt cotton, he added.
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