Entomologist says: Bollgard technology is a good fit with IPM system in cotton

Bollgard seed technology offers growers a good risk management tool for cotton pest control and gives them an option of managing insect control costs on the front end.

The opportunity becomes even better, said an Extension integrated pest management specialist, with the second generation Bollgard.

“We've seen higher (insect pest) mortality from Bollgard II,” said Roger Leonard, Louisiana State University entomologist.

Leonard said Bt cotton offers growers a useful tool in integrated pest management programs. The system takes on even more importance as growers and consultants identify bollworms resistant to pyrethroid insecticides.

“Adopting this technology has depended on the populations and cost to control caterpillar pests,” Leonard told a group of cotton consultants gathered in San Antonio recently for a southwest cotton technology seminar, sponsored by Bayer CropScience. “Lost yield to these pests also plays a role in adoption,” he said.

Bollgard adoption rate varies among states, ranging from about 9 percent to 90 percent. He said statistics show Texas at a 17 percent adoption rate with various areas of the state as low as 9 percent and some as high as 83 percent. Louisiana farmers plant about 90 percent of their cotton in Bollgard varieties. Oklahoma has nearly 60 percent in bt technology; New Mexico has 65 percent; Arkansas plants 85 percent of its cotton in Bollgard varieties; and Tennessee farmers plant about 85 percent Bt cotton.

High yield remains the number one concern for cotton variety selection, Leonard said. But newer varieties compare favorably with the parent lines from which they were bred, he said.

A critical advantage with Bollgard II is the broader spectrum of control. “We've seen control or suppression of a number of pests, including European corn borer (good control), tobacco budworm, fall armyworm, soybean loopers, salt marsh caterpillars and beet armyworm.”

He said corn earworms can be worse than the tobacco budworm. “So far, we still have effective insecticides for corn earworm, Orthene, for instance. But that will sometimes flare aphid and mite populations.”

He's also concerned about pyrethroid resistance. “We've seen some change in susceptibility (to pyrethroids insecticides) of tobacco budworm and bollworm in Louisiana,” he said. “We have not had field failures but if we had large enough populations we could see it.”

He said options such as Steward, Tracer and Denim are effective, but cost significantly more than pyrethroids.

“BG and BG II are good alternatives. Farmers have an added seed cost with the technology fees but they get value for the extra expense.”

He said BG and BGII outperform other systems. “BGII is best, but may not be immune to caterpillar damage. Growers need to determine if the damage is economical.”

In some cases, Leonard said, growers may justify an overspray on bt cotton to improve yield, but he cautions them to look closely at the bottom line. “They may increase yield but they may not do it economically.”

He said Bollgard II typically holds foliage-feeding caterpillars “way below economic levels.”

He said fall armyworm could cause some problems. “But even if growers have to overspray bt cotton, they will reduce the number of applications.”

Leonard said Bollgard cotton may allow growers to eliminate a broad-spectrum insecticide application but cautions them to watch for other pests to “fill the gap. Eliminating that broad-spectrum application creates an opening for new bugs — plant bugs, stinkbugs and such — because growers are using target-specific insecticides. These pests also creep in from other crops.”

He said material such as Trimax, Orthene and Diamond, with some pre-mix insecticides that include a pyrethroid and another product, are good options for these pests.

“Anticipate problems and then react appropriately,” he said.

Leonard said soil insecticide and seed treatments also help protect cotton early in the season. He said farmers who rely on technology to protect cotton from major pests can't forget the damage possible from thrips, aphids and other pests early in the season. He said a seed treatment or soil insecticide, followed by an early insecticide application, might prevent setbacks.

“Using Bollgard and Bollgard II still means farmers must follow accepted production practices,” Leonard said.

He said the Bt varieties may increase overall production efficiency, especially with an improved spectrum of control.

“This system offers an improved risk management tool for cotton farmers,” he said.

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