Submitted to: Government Publication/Report
Publication Type: Other
Publication Acceptance Date: 9/1/2006
Publication Date: 9/8/2006
Citation: Sappington, T.W., Christian, M.R., Heeringa, S.G., Fitt, G.P., Gould, F.L., Guse, C.A., Heckel, D.G., Hurley, T.M., Ives, A.R., Livingston, M.J., Portier, K.M., Schneider, J.C. 2006. SAP Minutes No. 2006-03 Final Report, A Set of Scientific Issues Being Considered by the Environmental Protection Agency Regarding: Analysis of a Natural Refuge of Non-cotton Hosts for Monsanto's Bollgard II Cotton. Posted on www.regulations.gov under EPA Document ID EPA-HQ-OPP-2006-0217-0042. 99 pages. Interpretive Summary:
Technical Abstract: There are many uncertainties, caveats, and assumptions evident throughout the modeling and analyses presented by Monsanto and revealed by the Panel discussion around the questions posed by EPA. Most of these by themselves might not in fact prove dangerous to IRM for cotton bollworm (CBW) and tobacco budworm (TBW), but collectively they represent unacceptably high levels of uncertainty, especially for the Mississippi Delta and East Texas regions. The validity, accuracy, and repeatability of the gossypol assay for identifying the non-cotton fraction of the TBW population is the single most important component of Monsanto's data presentation and argument for a natural refuge. Although the Panel received a description of the analytical technique, no member of the Panel had the required expertise in analytical chemistry to adequately review this new methodology. The Panel thus recommends a review of the technique by EPA staff. If the gossypol technique withstands critical scrutiny, the following comments will apply. The Panel has noted some potentially serious errors and biases in Monsanto's calculation of natural refuge for TBW and CBW that must be addressed. In addition, the Panel would prefer a more integrated and comprehensive statistical analysis of the spatial and temporal variability of refuge estimates and moth trap data to tease out crucial details regarding the appropriate spatial regions and the critical temporal periods that pose the most risk. Despite the potential biases, the Panel is in broad agreement that for the eastern parts of the Cotton Belt (Carolinas and Georgia), there are significant and reliable non-cotton refuges present that should be adequate to manage Bacillus thuringiensis (Bt) resistance in TBW associated with cotton systems involving Bollgard II, Bollgard, and Widestrike cotton. However, current evidence of adequate natural refuge in the Mississippi Delta and Texas regions is not convincing. Because resistance likely will evolve in areas with little effective refuge, such areas are of particular concern. When the estimated proportion of effective refuge for CBW and TBW is low (5-10%), higher levels of uncertainty attach to a number of assumptions and calculations for the proportion of effective refuge. Estimates of natural refuge (as corrected by the Panel) below 10% are not uncommon in the Midsouth, and all problems of uncertainty increase and compound each other when the estimated area of effective refuge is below 5-10%. Texas especially must be sampled more thoroughly, both spatially and temporally, to provide reliable estimates of the variation in production of TBW from alternative hosts that can be expected in different parts of the state during different times of the season. Only with this information can an informed judgment be made regarding the stability and adequacy of natural refuge.