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EPA approves Widestrike cotton trait

While WideStrike cotton may not “act” like Bt cotton as farmers currently know it, it should provide the same level of control as a full-season spray program for worms on cotton, according to university and company research.

WideStrike, a new, stacked insect-protection trait from Dow AgroSciences which expresses two Bacillus thuringiensis (Bt) proteins, Cry1F and Cry1Ac in cotton plants, received EPA approval Sept. 30.

According to Dow AgroSciences, WideStrike provides a high level of activity against worm pests such as cotton bollworm, tobacco budworm, beet armyworm, fall armyworm, soybean loopers, cabbage loopers and pink bollworm.

Current plans call for WideStrike to be available alone and also stacked with the Roundup Ready technology. Three WideStrike varieties will be available in 2005. In 2006, the WideStrike trait will be available in Roundup Ready Flex varieties.

Three years of company trials on 13 small plots comparing the WideStrike variety, PHY 440 W, and a conventional variety, PSC 355, indicated far less square damage for untreated WideStrike cotton versus conventional cotton (PSC 355), treated for worms. Unsprayed WideStrike yields were slightly higher than PSC 355 sprayed for worms. The highest yields were achieved on WideStrike cotton treated for worms.

At a recent field day announcing EPA approval of the WideStrike insect protection trait, Ralph Bagwell, LSU AgCenter entomologist, stressed that growers and consultants need to be aware of the differences between WideStrike and Bollgard technology.

“It's a live organism, and like any other live organism, it can throw you a curve ball,” Bagwell said. “We have a paradigm on transgenics based on our experiences with Bollgard. This one is different.”

Bagwell noted that Bollgard “starts off with higher expression in young tissue. It appears in WideStrike that the expression increases as tissue ages.”

Bagwell noted that in one WideStrike test plot, he found 16 percent worms in the terminals. “My expectations for WideStrike were based on my expectations for Bollgard. In Bollgard, worms will initiate in the blooms, work their way to bolls, and you're going to see some damage.”

But the worms in the WideStrike plot didn't make it to the bolls. “That's the big difference. Where we expect to take some boll damage in Bollgard and Bollgard II, we really didn't experience that in WideStrike.

“So, we'll have to sample WideStrike differently than we do Bollgard. There are going to be some steep learning curves for growers because the first inclination when you see worms in the terminals is to spray.

“At the end of the day, the technology is very effective,” Bagwell said. “It's unique. It's different.”

Bollworm pressure on the farm where the field day was held was extremely intense, according to Gus Lorenz, Arkansas Extension entomologist, who conducted a large plot test. There were dramatic differences in side-by-side plots of PHY 440 W untreated and PSC 355 untreated.

Angus Catchot, Extension entomologist, Mississippi State University, had two trials with WideStrike, one in the Hill area of Mississippi, another in the Delta, but did not have enough worm pressure to evaluate the technology this year at either site. “Agronomically, the PHY 470 W looked very sound.”

Scott Stewart, University of Tennessee Extension entomologist, has studied the technology for two years. “We had a moderate bollworm pressure for a two- to three-week period. The technology held up well against that pest and was very comparable to the other Bt technology.”

“We've also been able to reduce micronaire in these WideStrike varieties, compared to PSC 355,” said Bobby Haygood, product technology specialist with Dow AgroSciences. “One reason is the variety used to do the insertion has an Acala background, which gave breeders more opportunity to select for improved quality.”

Dow AgroSciences is seeking approval for refuge requirements for WideStrike cotton that are the same as those required for currently available Bt cotton.

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