No. 5 Article 1/May 7, 2010

"Refuge-in-the-Bag" Registration Approved by US EPA for Optimum AcreMax 1

On May 3, DuPont announced that the US Environmental Protection Agency (EPA) had approved the company's request for a seed mixture refuge for corn rootworms when planting Optimum Acre-Max 1 Pioneer corn hybrids (seed blend of 90% Herculex Xtra [Cry 1F + Cry34/35Ab1] and 10% Herculex I [Cry 1F]). The press release indicated that this new approach will be used in some producers' fields this year in preparation for the 2011 growing season. Farmers who elect to use Optimum Acre-Max 1 Pioneer corn hybrids will be able to reduce their corn rootworm refuge from the current structured 20% to a 10% seed mixture. According to the May 3 media alert, "In addition to the Optimum® AcreMax™ 1 product registration announced April 30, the EPA also has granted Pioneer registration for Optimum® AcreMax™ RW products, which integrate 90 percent Herculex® RW seed and 10 percent of a hybrid from the same genetic family without biotech insect protection. All seed in the bag is herbicide tolerant." Herculex RW corn hybrids express the Cry 34/35Ab1 binary proteins.

On April 30, the US EPA Office of Pesticide Programs, Biopesticides and Pollution Prevention Division, released a 33-page Biopesticides Registration Action Document titled Optimum®AcreMax™ B.t. Corn Seed Blends. A number of quotes from the document, which may shed some additional light on this significant development, follow.

This registration opens up a new chapter in the implementation of resistance management strategies designed to delay or prevent resistance development to Bt corn hybrids. This development raises many additional questions:

As I've indicated in earlier articles in the Bulletin, the early planting this season and favorable root establishment could help corn rootworm populations rebound from the past two seasons. Large root systems at the time of larval hatch (usually late May across central Illinois) could lower intraspecific competition for larval feeding sites and result in greater densities of western corn rootworms this year. I look forward to your reports this summer regarding how well corn rootworm products are performing.--Mike Gray

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