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Issue No. 9, Article 5/May 22, 2009

Scientific Advisory Panel Report on Pioneer's Optimum AcreMax Seed Mix Refuge (Refuge-in-a-Bag) Request Available On-Line

There have been many articles in the popular press about the outcome of discussions in February by a FIFRA Scientific Advisory Panel concerning their charge to evaluate the potential risks for resistance development by using a seed mix refuge of Optimum AcreMax for corn rootworm protection. Contrary to the tone of some of the articles, very significant challenges remain to implementing this concept for managing corn rootworm resistance, especially at the lower range of seed mixture refuges. The full report (meeting minutes) is available on-line (Adobe PDF). The overall report is quite lengthy and not an easy read. Provided below are quotes from the summary of panel discussions and recommendations (pp. 6-8 of the report).

  • "Overall, the Panel concluded that there are uncertainties with the scientific data supporting Pioneer's proposed seed blend, Optimum® AcreMaxTM1, and clear problems with reducing the refuge size."
  • "The Panel generally agreed that data presented by Pioneer and data found in the public literature provide no compelling evidence to reduce the proportion of non-Bt plants (either as a seed blend or spatial refuge) from 20% and there was strong concern with the request for any reduction in the refuge size with a seed blend of 5% or less."
  • "Data were not presented that supported a claim that potential yield losses justify a seed blend of no greater than 5%."
  • "The Panel supported the recommendation to conduct additional research with various percentages of seed mixtures to determine any effects on yield."
  • "Therefore, the Panel concluded that, based on the current science, it would be reasonable to commercially use 20% seed blend refuges while research suggested by the committee and other research projects are conducted to examine the performance of the seed blend strategy."
  • "The Panel agreed with EPA that there is uncertainty with regard to whether the mode of action of Cry34/35Ab1 is through a toxic or repellent mechanism."
  • "In summary, most Panel members believed that corn rootworm biology seems to lend itself to the seed blend concept and that while the seed blend refuge concept has merit, the Panel had concerns regarding the reduction in refuge size. However, the Panel also believed that it is vital to preserve the Bt CRW biology and was significantly concerned about the proposal to move to both a seed blend refuge and a drastic reduction in refuge at the same time."

This report offered by the Scientific Advisory Panel is just that--advisory. The US Environmental Protection Agency will offer a full response later this year regarding this request for a new approach to resistance management for corn rootworms.--Mike Gray

Author:
Mike Gray

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