Monsanto and Dow AgroSciences Complete Regulatory Authorizations for SmartStax^TM Corn Hybrids

Eileen Cullen, Extension Entomologist

Monsanto and DowAgroSciences, in a cross-licensing agreement, announced on July 20 that they have received registration approval from the U.S. Environmental Protection Agency (EPA) and a regulatory authorization from the Canadian Food Inspection Agency (CFIA) to commercialize SmartStax^TM corn hybrids in 2010. The hybrids will express the following insecticidal proteins: Cry3Bb1 (event MON88017), Cry34/35Ab1 (event DAS-59122-7), Cry1F (event TC 1507), and Cry1A.105+Cry2Ab2 (event MON89034).

In addition to targeting corn rootworms and the lepidopteran complex, SmartStax^TM hybrids will provide herbicide tolerance to glyphosate and glufosinate. The US EPA and CFIA approvals will enable producers in the US Corn Belt and Canada who use the hybrids to reduce refuge size from 20% to 5%. Cotton Belt producers will be able to reduce their refuges from 50% to 20%. In a joint news release, the companies indicated they intend to introduce SmartStax^TM hybrids across 3 to 4 million acres in 2010.

Extension entomologists learned about the new regulatory authorizations, at the time of the July 20 press release. Some take home points for now are summarized below.

• The U.S. EPA approval took into account data on the “pyramid” strategy of a transgenic crop producing 2 different Bt toxins targeting the same pest. For example, in the SmartStax^TM case, Cry3Bb1 and Cry34/35Ab1 both target corn rootworms, while Cry1F and Cry1A.105+Cry2Ab2 both target the lepidopteran pest complex. Multiple modes of action for corn rootworm and multiple modes of action for the lepidopteran pest complex are a factor in reduced structured refuge size and long-term durability of corn Bt insect trait technologies. This “pyramid” strategy is based on the concept that selection for resistance to 1 toxin does not cause cross-resistance to the other toxin (e.g., because the Bt toxins bind to different larval midgut target sites).                                                                                       

• A “stacked” trait is not necessarily a “pyramided” trait. For example, currently reginstered Bt corn hybrids with a single Bt corn rootworm trait, a single Bt lepidopteran trait, and a herbicide tolerance trait are commonly referred to as “stacked trait” hybrids. 

• Refuge reduction from 20% to 5% is not authorized for existing single trait Bt corn hybrids or those stacked trait hybrids that combine single traits for corn rootworms and Lepidoptera (see bullet point above).

• SmartStax^TM regulatory approval for 2010, with its reduced refuge from 20% to 5% is not “refuge in the bag” Optimum AcreMax 1 or Optimum AcreMax 2. Pioneer Hi-Bred International has sought approval for seed blends and refuge reduction, but this, to the best of my and my North Central Region Extension Entomologist colleagues’ knowledge and communications with government and industry, is still pending EPA approval and has not been approved at this time.