February 29, 2008
There's little doubt that U.S. corn growers like biotech corn for control of both above- and below-ground insect pests. Trouble is, refuge management strategies aimed at preventing insect resistance have become troublesome to handle. Each producer of these high-tech crops is considering their own approach to this issue, and during Commodity Classic this week Pioneer Hi-Bred, a DuPont business, announced its strategy.
This week the company submitted a proposal to the U.S. Environmental Protection agency that would put the refuge right in the bag. The approach, which will roll out in two phases, would offer growers options for control of these pests with a simpler approach to achieving an acceptable level of residue.
Phase 1, which should be available for the 2009 season is Optimum AcreMax 1. "We're looking for this concept to have reduced refuge to improve the productivity and use of Herculex," says Frank Ross, Pioneer vice president, North American Operations. "For the first time, farmers will be able to plant all their acres wit a single product that satisfies refuge requirements."
AcreMax 1 would eliminate the need to plant a separate corn rootworm refuge. Pending regulatory approval, the first phase will be a combination of a base hybrid with the Herculex Xtra trait and that same base hybrid with the Herculex I trait - all in the same bag. This approach would reduce the need to plant a separate rootworm refuge.
All seeds in this package will be glyphosate and glufosinate tolerant and treated with an insecticidal seed treatment that protects from secondary pests.
Phase 2, which the company hopes to have available by 2011, is Optimum AcreMax 2 which would add the YieldGard cornborer gene with Herculex Xtra, offering two modes of action for above-ground pests. EPA has indicated, in the past, that two modes of action in the same field may be acceptable as a refuge strategy, but the concept is still subject to regulatory approval.
This second-phase approach would extend the integrated refuge strategy to include corn borer and allow growers to meet all refuge requirements in a single product. The aim is to have a low level refuge integrated in the product mix to increase yields, simplify compliance and eliminate the need for a separate block or strip refuge.
Part of the approach to EPA is to prove that the new refuge strategy is effective in preventing resistance. The company is actually proposing a reduction in the size of the refuge - the level is not being published - and incorporating it into the bag. This allows for easier management.
A look at Phase 1
A grower that plants Optimum AcreMax 1 would have two different options for refuge management. Since the corn rootworm refuge is managed in the bag, growers would have the option of planting their corn borer refuge within a half-mile of the field. That would mean filling the planter with Optimum AcreMax 1 and planting the field, then planting the refuge crop in a separate operation.
With Option 1 - Separate refuge: By satisfying the CRW refuge in the bag, Optimum AcreMax 1 would allow growers to place the required corn borer refuge in a different field, up to one-half mile away.
Option 2 with this program would be to plant 80% of the field to Optimum AcreMax 1, then utilize a Pioneer hybrid with Herculex RW to serve as the 20% refuge. That gives the grower 100% in-plant rootworm coverage in the field while meeting the corn borer refuge requirement.
With Option 2 - offering 100% rootworm coverage: With CRW refuge integrated into the bag, growers could plant 80% of the field to Optimum AcreMax 1 and utilize a Pioneer hybrid with Herculex RW to serve as the 20% corn borer refuge resulting in 100% in-plant CRW coverage in the field.
"I think growers will most likely opt for the first choice," says Bill Neibur, DuPont vice president, Crop Genetics Research and Development. "They can just fill the planter and go in that single field, then plant the refuge in another field."
Phase II approach
Bringing in a totally different mode of action for corn borer control - YieldGard uses a different Bt protein for corn borer than Herculex - may be an acceptable approach to corn borer refuge right in the field. This could eliminate the need for that 20% refuge, when combined with the in-the-bag approach to corn rootworm control.
Optimum AcreMax2 would offer two different approaches - a combined corn rootworm and corn borer solution, or a corn borer version. The CRW-ECB version would include Herculex Xtra and YieldGard Corn Borer together. The ECB version would be Herculex I and YieldGard. Each would contain a small amount of refuge seed mixed into the bag to provide a full in-field solution without planting separate refuge.
Add in that Pioneer and Syngenta are teaming up to utilize mir162 for control of added in-field above-ground pests and Pioneer believes it will be offering even higher crop protection with easier management in the future. That added insect protection could be available as early as 2013 - pending regulatory approval.
"We've heard from customers of the last five years how difficult it is to deal with the refuge, and their concern about the degradation of yields or plants not protected with insecticide traits," Neibur says. "We hope that EPA will study this and come to the same conclusions we have about refuge."
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