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Bug-killer Cotton Cutting Pesticide Use

Georgia farmers are using a new way to grow cotton that keeps bugs at bay while protecting the environment.

They're growing a new type of cotton, called Bt cotton, that fights some insects while it grows.

Phillip Roberts, an entomologist with the University of Georgia Extension Service, expects Georgia farmers to plant about a third of the 1997 cotton crop to Bt varieties.

Farmers include Bt cotton, Roberts said, in an overall insect-control method called integrated pest management.

IPM programs use all sorts of natural controls, including Bt cotton and beneficial insects, instead of chemicals to keep insects from harming the crop. Cotton growers may still have to use some pesticides, but only as a last resort.

IPM helps farmers stay on friendly terms with people who live around them, too. It can cut down on the number of times farmers must spray pesticides. Neighbors like that.

Bt cotton can cut out even more spraying. It produces its own natural toxin that helps control certain insects on the plant.

Scientists took a toxin-producing gene from bacteria called Bacillus thuringiensis (Bt). They inserted it into the new cotton plant that takes its name.

The naturally produced toxin helps control insects. "Bt cotton and IPM programs don't guarantee 'no sprays,'" said Steve Brown, an extension cotton agronomist. "But they can dramatically decrease the number of applications required."

Killing bugs with the Bt toxin isn't new. Many gardeners use it, too. Laboratories collect the toxin and include it in foliar sprays for garden plants. The toxin is the same. Only the delivery method differs.

Now that the Boll Weevil Eradication Program has banished weevils from Georgia cotton fields, Roberts said farmers can really take advantage of the Bt technology.

"Regular cotton varieties might require six or seven pesticide applications in a given year to control insects," he said. "A field of Bt cotton right next to the regular variety may only need two or three applications for the same amount of insect control."

One concern many people have is that insects may become resistant to pesticides. Gary Herzog, a research entomologist at the Coastal Plain Experiment Station, said IPM and Bt cotton can slow that process.

Herzog has studied insect pesticide resistance trends since 1979.

"Usually, a particular chemical can be widely used for about 10 years before resistance shows up," he said.

Bt cotton can extend that time. Farmers don't have to spray as often. So insects aren't exposed as much to the most commonly used pesticides. So it takes them longer to develop resistance.

If the Bt toxin doesn't kill all the insects, Herzog said, it still weakens survivors. That makes them more vulnerable to other insecticides and the beneficial insects that prey on them.

The Bt toxin doesn't affect the cotton fiber. It's as strong and long and white as that of non-Bt varieties.

Planting Bt cotton can help farmers' profits, too. If they can grow cotton with lower cost per acre, they can make more money on the same land.

Higher profits lead more farmers to grow cotton. When more cotton is sold, though, the farmer's prices can drop. Retail cotton clothing prices can drop, too.

It costs farmers more -- about $33 per acre -- to plant Bt cotton. Roberts and Brown said if a grower has to spray a field four or more times for bollworms, he may do better planting Bt cotton.

"Each farmer has to decide if he can control bollworms for less than the cost to plant Bt cotton," Brown said.

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