Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/21/2010
Publication Date: 1/30/2011
Citation: Onstad, D.W., Mitchell, P.D., Hurley, T.M., Lundgren, J.G., Porter, R.P., Krupke, C.H., Spencer, J.L., Difonzo, C.D., Baute, T.S., Hellmich Ii, R.L., Buschman, L., Hutchinson, W., Tooker, J.F. 2011. Seeds of change: corn seed mixtures for resistance management and IPM. Journal of Economic Entomology. 104(2):343-352. Interpretive Summary: Farmers that plant Bt corn are required to devote a portion of their acreage to non-Bt varieties in order to stave off the evolution of Bt-resistance in predominant pests (especially European corn borer and corn rootworms.) These block refuges function by allowing Bt-susceptible individuals the chance to mate with any Bt-resistant individuals that may emerge from neighboring Bt fields, and thus diffuse resistance genes within the population. Recently, the US Environmental Protection Agency has authorized the use of seed mixtures (Bt and non-Bt seeds in the same bag) for use in commercial production. This commentary raises many questions about the efficacy of this strategy. We conclude that seed mixtures will make monitoring key pests more difficult, and that seed mixtures may make insect resistance management riskier because of the numerous aspects of pest biology that are simply unknown. On the other hand, seed mixtures may be preferred over block refuges because farmers are reluctant to plant large blocks to non-Bt hybrids. The overall conclusion of the discussion is that many questions remain regarding the evolution of insect resistance, and data voids like these may affect how well block refuges and seed mixtures function.
Technical Abstract: The use of mixtures of insecticidal seed and non-toxic seed to provide an in-field refuge for susceptible insects in an insect-resistance-management (IRM) plan has been considered for at least two decades, but the US Environmental Protection Agency has only recently authorized their use in commercial production. The purpose of this commentary is to explore issues that regulators, industry and other stakeholders should consider as we expand the use of biotechnology and consider the use of seed mixtures as a major tactic in IRM. We discuss how block refuges and seed mixtures in transgenic insecticidal corn production will impact integrated pest management (IPM) and the evolution of pest resistance. We conclude that seed mixtures will make pest monitoring more difficult. We also conclude that seed mixtures may make IRM riskier because of larval behavior and greater adoption of insecticidal corn. On the other hand, block refuges are riskier because of adult pest behavior and the lower compliance with IRM rules expected from farmers. It is likely that secondary pests not targeted by the insecticidal corn as well as natural enemies will be handled differently in block refuges and seed mixtures.