Sandy Stewart had some good news and some not so good news about varieties containing the new Roundup Ready Flex technology at Cotton Incorporated’s Crop Management Seminar in Memphis, Tenn.

Stewart, Burch associate professor and Extension cotton specialist with the LSU AgCenter, was reporting on the performance of the Roundup Ready Flex and Bollgard II/Roundup Ready Flex stacked-gene varieties in 2006.

“On average, the new Flex introductions have better fiber quality than the varieties we’ve been growing the last several years,” he said, referring to the technology that allows growers to spray glyphosate over-the-top of resistant varieties up until a few days before harvest.

The not so good news? The Roundup Ready Flex or Bollgard II/Roundup Ready Flex varieties don’t always yield as well as some of the older transgenic cotton.

“A lot of people ask how much yield can we give up with Flex cotton?” said Stewart. “I’d be willing to go out on a limb and say it could be as high as 200 pounds. But it can also be from zero to 100 if you plant the right variety.

“We will gain some cents on quality. In terms of loan value, these new varieties will go a little higher than Deltapine 555 BG/RR or Stoneville 5599 BG/RR. But there are no Flex varieties right now that will physically out-yield the best Bollgard-Roundup Ready varieties.”

That doesn’t mean growers are likely to shy away from the Roundup Ready Flex varieties or that the yield gap between Bollgard/Roundup Ready and Flex varieties won’t narrow as more growers transition into the Flex system.

Stewart said only 10 percent of Louisiana’s cotton acreage was planted to varieties containing the Roundup Ready Flex technology in 2006. But many of the state’s growers “tried a little.”

“The growers I’ve talked to and those who have visited with my colleagues around the Mid-South were happy with the weed control from the Roundup Ready Flex system. By the middle of the summer, people were talking about how many fewer hands they might have to employ if they had a total Flex system.”

At the beginning of the season, Stewart said, many growers were saying the new Flex varieties had to yield with Deltapine 555. “By late August, they were saying these new varieties have to yield. I think that’s very telling.”

He said four or five varieties appear to have risen to the top of the 2006 on-farm Roundup Ready Flex trials in Louisiana. Those include Deltapine 117 B2RF, Stoneville 4554 B2RF, Phytogen 485 WRF and Phytogen 425 RF.

“It seems like anytime you introduce a group of new transgenics, a handful will be the cream of the crop. Based on discussions with my colleagues in Mississippi, in particular, they’re seeing the same thing.”

Deltapine 117 was in the top four varieties in each of the six on-farm locations in Louisiana with one exception.

“This was in Red River Parish,” said Stewart. “It was non-irrigated and it was severely drought-stressed. Everything around there picked about 1,200 pounds per acre, but this grower simply did not catch a rain.

“In this particular trial, we included Deltapine 555. It was a sandy soil and it was drought-stressed and 555 just basically cleaned house. DP 117 B2RF was the earliest variety we had, and it finished near the bottom in this location.”

Stoneville 4554 B2RF, which finished a close second across all the on-farm Flex trials, “appears to be one of the most consistent varieties and one of the most manageable across a lot of environments.” Stoneville 4554 finished in the top four in the on-farm Flex trials.”

Phytogen 485 WRF also yielded well across many soil types while DP 143 B2RF and DP 164 B2 RF, both full-season varieties, produced good yields and good fiber quality.

While the varieties containing the Flex technology may not yield as well as the older transgenics, Stewart believes it’s just a matter of time until Roundup Ready Flex and Bollgard II/Roundup Ready Flex varieties dominate the landscape.

“Whether it’s the convenience or the weed control, for a lot of different reasons, farmers like Roundup Ready Flex,” he said. “I think we’re going to transition into the Flex system in the next two or three years. “The comparison with DP 555BG/RR may be important, but in two or three years I don’t think it will matter.”

Stewart says he does have some issues about the transition. One involves the growing number of entries in the official variety trials conducted by the land grant universities in the cotton-growing states.

“We had 43 early varieties and 26 medium to full-season varieties in the Louisiana OVT trials this past year,” he noted. “It is very difficult to come up with a meaningful evaluation when you’re testing 69 varieties.”

Many of those varieties may never be important to farmers in Louisiana, he said. “I think we need to revisit the official variety trial concept to make sure we provide the information farmers need about varieties that are economically important.”

Another issue involves the confusion over the number of brand names that contain the same genetic material from Monsanto. Stewart listed five different brand names that contain the same genetic transformation event, 450001G, for example.

Growers are also concerned about the continuing consolidation in the cottonseed business and that one company is the primary source of the Roundup Ready Flex technology. A big question, he said, is how competitive Stoneville Seed Co., which Monsanto has promised to sell if it completes its proposed acquisition of Delta and Pine Land Co., will be in 2008.

“And growers can’t help but wonder about the increased reliance on Roundup Ready and Roundup Ready Flex technology in a world having to deal with an increasing number of glyphosate-tolerant weeds.”

e-mail: flaws@farmpress.com