Growers and consultants participating in on-farm trials with Roundup Ready Flex and Bollgard II cotton are also working with a new formulation of Monsanto’s glyphosate or Roundup herbicide.

The new formulation — MON 3539 — was developed after Monsanto determined that some of the components in existing glyphosate formulations, including Roundup agricultural brands, can cause leaf injury when applied past the four-leaf stage.

About 160 growers and consultants from across the Cotton Belt are participating in trials with Bollgard II and Roundup Ready Flex cotton this year. Monsanto representatives say they expect to conduct a full commercial launch of the Roundup Ready Flex technology in 2006.

“We want growers to have the best experience possible with the new technology,” said Sarah Vacek, Roundup marketing manager. “We did not want to launch Roundup Ready Flex and have growers wondering what was happening with the leaf injury.”

Vacek discussed the new formulation and the leaf injury symptoms at a Monsanto Cotton Media Briefing in St. Louis.

Roundup Ready Flex is the name given to the second generation of Monsanto’s breakthrough herbicide-resistant, Roundup Ready cotton technology. Any registered Roundup herbicide formulation can be sprayed over the top of RR Flex varieties past the four-leaf stage and up to seven days before harvest.

“Roundup Ready Flex cotton will allow growers to spray Roundup herbicide registered for use throughout the cotton growing cycle,” said Vacek. “The new Roundup Ready cotton has increased tolerance to glyphosate during cotton reproductive stages.”

After observing the leaf injury symptoms in a few plants sprayed at the four-leaf stage, Monsanto scientists “began conducting exhaustive research to determine what could be done to prevent the injury,” she said.

As part of those efforts, researchers began developing new Roundup formulations that would not cause the symptoms, which include a grayish pattern on affected leaves. One of those formulations, MON 3539, is being used by growers in on-farm trials with Roundup Ready Flex and Bollgard cotton this season.

“We have not had any confirmation of yield reduction when the leaf injury symptoms occur,” she said. “But we want to make sure growers don’t see any problems when they apply Roundup herbicide over the top of Roundup Ready Flex cotton.”

For the 2006 season, Monsanto will make the new formulations broadly available to support grower choice and a competitive market place. “The new Roundup formulations will be offered at price points similar to today’s products to earn grower business,” said Vacek.

MON 3539 herbicide is the only Monsanto herbicide currently labeled for those applications. It is not registered for sale or use in California.

“No one takes weed control and crop safety more seriously than Monsanto,” notes Vacek. “As soon as the crop response was confirmed, we initiated research to determine the cause and then to identify solutions. We are continuing rigorous research to explore all possible solutions so that we can bring the best solution for growers next year.”

The 160 growers and their consultants are growing Roundup Ready Flex and Bollgard II cotton on about 3,000 acres from Virginia to California, according to Dave Rhylander, director of traits for Monsanto.

“These field trials are designed to give a large number of growers and consultants a firsthand look at Bollgard II with Roundup Ready flex technologies under actual, on-farm conditions,” he said. “We want these growers to share their observations and results with other growers in their area who have an interest in these technologies.”

The Roundup Ready Flex system would offer benefits beyond the more flexible application window, said Chad LeBlanc, Monsanto’s cotton marketing manager.

“Not only does Roundup Ready Flex offer season-long herbicide applications, but it also provides growers with excellent crop safety for glyphosate applications past the four-leaf stage, reduced production risk and the ability to tailor herbicide applications to weeds instead of the crop stage.”

That expanded window of application will also afford growers an opportunity to tank mix approved glyphosate herbicide with other crop protection products, including insecticides, other herbicides and plant growth regulators. “This flexibility will save spray trips over the field and result in more efficient management,” said LeBlanc.

Roundup Ready Flex cotton is fully approved for food and feed use in the United States, he said, and is awaiting approval in key export markets. Monsanto expects Roundup Ready Flex cotton will be offered in time for the 2006 growing season as a single-trait product and in combination with other traits, such as Bollgard II.