Cotton producers from Texas to the East Coast can begin relying on a “natural refuge” to help forestall the development of insect resistance to the Bollgard II gene after EPA approved a request for such an option from Monsanto.
Until now, farmers in those regions have been required to plant a 5 percent “unsprayed” or 20 percent “sprayed” refuge of non-Bt cotton for each 100 acres of Bollgard or Bollgard II cotton they planted. Those requirements will remain in effect for Bollgard cotton and for farmers in selected Texas counties
EPA said the current, structured refuge constraints will continue for pink bollworm resistance management in 15 counties in the trans-Pecos area of Texas, Arizona, New Mexico and California.
“This is great news for U.S. cotton producers in eligible regions who choose to plant Bollgard II cotton,” said Walt Mullins, Monsanto technology development manager. “It allows them to simplify their pest control program by using cotton technology with two effective Bt genes.”
EPA said it made the decision after “careful scientific review” had shown that insect resistance management could be accomplished by using only alternative crops and weeds in combination with plantings of Bollgard II cotton from Texas to the mid-Atlantic region.
“The agency’s approval comes after extensive analyses and peer review of Monsanto Company’s 2006 natural refuge proposal for Bollgard II cotton,” it said in a Pesticide Program Update.
“EPA concluded that scientific evidence showed using the natural refuge with Bollgard II cotton would be effective for areas where tobacco budworm and cotton bollworm were primary pests.”
Not everyone involved in cotton production was happy with the change. Entomologists and crop specialists in Louisiana have opposed the natural refuge option.
“Our position hasn’t changed,” said Sandy Stewart, Extension cotton specialist with the LSU AgCenter. “We’re the only state that expressed rather strongly that we need to evaluate more data to determine whether or not a natural refuge is the best way to manage insect resistance.
“Resistance management has become such a huge issue for cotton producers, whether it’s Bt cotton, neonicotinoids, aphids, plant bugs or herbicide resistance,” said Stewart. “We have to manage the entire system with resistance in mind.”
In its request for a natural refuge, Monsanto said Bollgard II cotton contains two different plant-incorporated protectants (PIP), Cry2Ab2 and Cry1Ac Bt proteins that are effective in controlling insect pests that include tobacco budworm, cotton bollworm, pink bollworm, loopers, and armyworms.
“Use of Bollgard II cotton, with its two distinct Bt proteins, in conjunction with the use of a natural refuge, will enhance cotton insect resistance management,” EPA officials said in its Pesticide Program Update.
Researchers who support the natural refuge concept say they’ve seen scientific evidence tobacco budworms and bollworms can move to cotton from a large number of alternative crop and native host plants.
“We have good data from North Carolina and Georgia that show tobacco budworm can be found living on a number of crops and other plants,” said J.R. Bradley, a researcher at North Carolina State University. The data came from tests, using carbon isotopes and gossypol analysis to determine the insects’ larval food sources, which were conducted in seven cotton-producing states.
But some Louisiana entomologists are concerned about how well the research results translate across all the regions where the new natural refuge option will be available to growers.
“I’m in disbelief that they did it (issued the approval),” said Ray Young, a consultant from Wisner, La. “I don’t understand it. It’s going to be hard to prove to us that there is enough natural refuge out there. I just don’t totally trust all the research.”
Young said he first started dealing with resistance in 1955 when boll weevils were no longer controlled by chlorinated hydrocarbons. “We were going great guns, and all of a sudden, we weren’t controlling them. The whole nation said we were wrong. They said we did poor entomology, it rained too much, on and on they went. But in 1956, they said, ‘You guys were right.’”
Young said the shift from Bollgard/Roundup Ready varieties to Bollgard II/Flex varieties will happen whether or not there is natural refuge. “It’s easier to raise and costs a little less to produce. And the quality on some of these new Bollgard II/Flex varieties is a notch above.”
Farm groups in other states have supported removing the structured 5 percent or 20 percent refuge options — which required growers to plant blocks of non-Bt cotton in close proximity to Bt — because of concerns that the requirement was costing growers yield.
In some cases, the issue has caused splits between the farm organizations and the research community in their respective states.
Young said he believes the yield loss from structured refuges has been exaggerated.
“With the 5-percent embedded refuge, we haven’t taken a hit on yields,” he said. “When you get worms in the refuge, they move out in the non-refuge cotton, but you don’t have moths moving from the non-refuge cotton into the refuge cotton. You have a dilution factor there because they move out, but they don’t move in.”
The natural refuge option applies to Bollgard II cotton planted in the states of Alabama, Arkansas, Florida, Georgia, Kansas, Kentucky, Louisiana, Maryland, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas (excluding the following counties: Brewster, Crane, Crockett, Culberson, El Paso, Hudspeth, Jeff Davis, Loving, Pecos, Presidio, Reeves, Terrell, Val Verde, Ward, and Winkler), and Virginia.
EPA previously established prohibitions on the planting of Bt cotton in the Texas Panhandle counties of Carson, Dallam, Hansford, Hartley, Hutchinson, Lipscomb, Moore, Ochiltree, Roberts and Sherman as well as south of Highway 60 in Florida. These restrictions do not change with the approval of natural refuge for Bollgard II cotton.