Field Assessment of Insect Resistance Management (IRM) for Plant-Incorporated-Protectants (PIPs)

Objective/Intended Use

The goal is to develop field methodologies to assess and monitor the impacts of insect resistance management strategies (high-dose/structured refugia) on the long-term susceptibility of the targeted pests.

Abstract

The development of target pest resistance to the products of transgene[s], e.g., plant-incorporated protectants is a serious risk both to the sustainability of these crops and to the wider utility of environmentally soft microbial pesticides. Therefore, the EPA requires growers of PIP crops to follow a high-dose/structured refugia strategy to delay or prevent resistance development. This marks the first time the EPA has required resistance management as part of a pesticide registration. Effective management requires sensitive tools for detecting resistance development in field pest populations early enough to allow for corrective action. The research is composed of two parts, each involving the development and refinement of field-based methodologies to assess and manage insect resistance in the field. One component will focus on field testing and validation of the management strategy for a crop containing a bacterial gene that produces a protein toxic to certain insect pests. Key assumptions of the models upon which this strategy is based still have not been empirically tested in field populations of the target pests. Significant data gaps exist regarding pest biology, ecology and population dynamics, particularly with respect to dispersal and use of alternate hosts. Target pests may include key lepidopteran cotton pests, Heliothis virescens and Pectinophora gossypiella; Helicoverpa zea, a pest of both cotton and corn; and on corn specifically, the lepidopteran pest, Ostrinia nubilalis and two beetle pests, Diabrotica barberi and D. virgifera. A second research component will focus on assessing appropriate tools to identify and measure insect resistance in field populations of the target pests. These tools include both functional screens or bioassays and molecular markers. Preliminary markers have been developed for H. virescens and P. gossypiella, but are still being tested in field populations. The information provided is intended for use in future risk assessments of similar biotechnology products. Citations: Luttrell, RG and MI Ali. 2007. Exploring Selection for Bt Resistance in the Heliothines: Results of Laboratory and Field Studies. in Proceedings of the 2007 Beltwide Cotton Conferences, New Orleans,LA. January 9-12, 2007. (Boyd, S., Huffman, M., Richter, D. & Robertson, B. eds) 1073-1086 (National Cotton Council of America, Memphis, TN; 2007). T.J. Stodola and D.A. Andow. 2004. F2 screen variations and Associated Statistics. J. Econ. Entomol. 97(5): 1756-1764, 2004 Stodola, T. J., D. A. Andow, A.R. Hyden, J. L. Hinton, J. J. Roark, L. L. Buschman, P. Porter and G. B. Cronholm. 2006. Frequenct of resistance to Bacillus thuringiensis toxin CrylAb in southern US Corn Belt population of European corn borer (Lepidoptera: Crambidae). J. Econ. Entomol. 99(2): 502-507.

Project Status

Begin late in fiscal year 2003.