Estimating the effects of Cry1F Bt‐maize pollen on non‐target Lepidoptera using a mathematical model of exposure
1. In farmland biodiversity, a potential risk to the larvae of non‐target Lepidoptera from genetically modified (GM) Bt‐maize expressing insecticidal Cry1 proteins is the ingestion of harmful amounts of pollen deposited on their host plants. A previous mathematical model of exposure quantified this risk for Cry1Ab protein. We extend this model to quantify the risk for sensitive species exposed to pollen containing Cry1F protein from maize event 1507 and to provide recommendations for management to mitigate this risk.
2. A 14‐parameter mathematical model integrating small‐ and large‐scale exposure was used to estimate the larval mortality of hypothetical species with a range of sensitivities, and under a range of simulated mitigation measures consisting of non‐Bt maize strips of different widths placed around the field edge.
3. The greatest source of variability in estimated mortality was species sensitivity. Before allowance for effects of large‐scale exposure, with moderate within‐crop host‐plant density and with no mitigation, estimated mortality locally was <10% for species of average sensitivity. For the worst‐case extreme sensitivity considered, estimated mortality locally was 99·6% with no mitigation, although this estimate was reduced to below 40% with mitigation of 24‐m‐wide strips of non‐Bt maize. For highly sensitive species, a 12‐m‐wide strip reduced estimated local mortality under 1·5%, when within‐crop host‐plant density was zero. Allowance for large‐scale exposure effects would reduce these estimates of local mortality by a highly variable amount, but typically of the order of 50‐fold.
4. Mitigation efficacy depended critically on assumed within‐crop host‐plant density; if this could be assumed negligible, then the estimated effect of mitigation would reduce local mortality below 1% even for very highly sensitive species.
5. Synthesis and applications. Mitigation measures of risks of Bt‐maize to sensitive larvae of non‐target lepidopteran species can be effective, but depend on host‐plant densities which are in turn affected by weed‐management regimes. We discuss the relevance for management of maize events where cry1F is combined (stacked) with a herbicide‐tolerance trait. This exemplifies how interactions between biota may occur when different traits are stacked irrespective of interactions between the proteins themselves and highlights the importance of accounting for crop management in the assessment of the ecological impact of GM plants.
Document Type: Research Article
Affiliations: 1: Oaklands Barn, Lug’s Lane, Broome, Norfolk NR35 2HT, UK 2: European Food Safety Authority, GMO Unit, Largo Natale Palli 5/A, IT-43121 Parma, Italy 3: Italian National Agency for New Technologies, Energy and Environment, Research Centre Trisaia, IT-75026 Rotondella, Italy 4: Federal Office of Consumer Protection and Food Safety, Mauerstrasse 39-42, DE-10117 Berlin, Germany 5: CEH-Wallingford, Maclean Building, Crowmarsh Gifford, Wallingford, Oxon OX10 8BB, UK 6: Aarhus University, NERI, Department of Environmental Chemistry and Microbiology, Frederiksborgvej 399, DK-4000 Roskilde, Denmark 7: Szent István University, Plant Protection Institute, Pater K. 1, HU-2100 Gödöllo˝, Hungary 8: INRA, Unité Eco-Innov, BP1 Campus de Grignon, FR-78850 Thiveral-Grignon, France 9: Büro für Landschaftsökologie und Umweltstudien, Muehlenweg 60, D-29358 Eicklingen, Germany 10: Università di Pisa, Facoltà di Agraria, Dipartimento di Biologia delle Piante Agrarie, Via del Borghetto 80, IT-56124 Pisa, Italy 11: Sweet Environmental Consultants, 6 The Green, Willingham, Cambridge CB24 5JA, UK 12: Johann Heinrich von Thünen-Institute, Institute for Biodiversity, Bundesallee 50, DE-38116 Braunschweig, Germany
Publication date: February 1, 2012