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Scientific Opinion supplementing the conclusions of the environmental risk assessment and risk management recommendations for the cultivation of the genetically modified insect resistant maize Bt11 and MON 810
The EFSA GMO Panel was asked by the European Commission to apply its mathematical model to simulate and assess potential adverse effects resulting from the exposure of non-target Lepidoptera to maize Bt11 or MON 810 pollen under hypothetical agricultural conditions, and to provide information on the factors affecting the insect resistance management plan, additional to that in its 2011 Statement supplementing the evaluation of the environmental risk assessment and risk management recommendations on insect resistant genetically modified maize Bt11 for cultivation. Here, risk managers are provided with additional evidence and further clarifications to those previous conclusions and risk management recommendations. This Scientific Opinion provides background scientific information to inform the decision-making process; the EFSA GMO Panel reiterates that risk managers should choose risk mitigation and management measures that are proportionate to the level of identified risk according to the protection goals pertaining to their regions.
© European Food Safety Authority,2012
In its 2011 Statement supplementing the evaluation of the environmental risk assessment and risk management recommendations on genetically modified insect resistant maize Bt11 for cultivation, the EFSA GMO Panel used the mathematical model, initially developed for maize MON 810 and later recalibrated for maize 1507, to simulate and assess potential adverse effects resulting from the exposure of non-target (NT) Lepidoptera (butterflies and moths) to pollen from maize Bt11 under representative EU cultivation conditions. The model was also used to estimate the efficacy of certain mitigation measures. The EFSA GMO Panel concluded that risk mitigation measures may be needed under specific conditions (depending on e.g., sensitivity and occurrence of NT Lepidoptera, acreage of Bt-maize, host-plant density) in order to reduce the exposure of extremely sensitive NT Lepidoptera to maize Bt11 pollen. The EFSA GMO Panel considered that the conclusions on the risk to NT Lepidoptera from maize Bt11 apply equally to maize MON 810. The EFSA GMO Panel also reiterated its recommendation that appropriate insect resistance management (IRM) strategies relying on the ‘high dose/refuge’ strategy should be employed, in order to delay the potential evolution of resistance to the Cry1Ab protein in lepidopteran target pests.
In this Scientific Opinion, the EFSA GMO Panel was asked by the European Commission to re-apply its mathematical model to consider additional hypothetical agricultural conditions, and to provide more information on the factors affecting the IRM plan, in order to supplement its 2011 Statement on maize Bt11. Here, risk managers are provided with additional evidence and further clarifications to those previous conclusions and risk management recommendations.
Depending on the level of exposure to Bt-maize pollen, there is a potential hazard to NT lepidopteran larvae on their host-plants in fields cropped with non-Lepidoptera-active crops when they neighbour the maize Bt11/MON 810 field under consideration. However, the need for risk management should consider the distance from the nearest source of Bt-maize pollen and hence their exposure as well as the pest status of the species concerned.
Within agricultural landscapes, when a field cropped with maize Bt11/MON 810 has no margins containing host-plants of NT lepidopteran larvae, the only larvae exposed are those on any host-plants occurring within the GM crop. When such host-plants are present, a greater percentage of the larvae exposed to Bt-maize pollen are expected to suffer mortality than when a field has margins with host-plants.
If a maize Bt11/MON 810 field has margins, then sown strips of non-Bt-maize, placed between the edges of the Bt-maize crop and each margin, are considerably more effective as a mitigation measure at reducing expected mortality than a single block of non-Bt-maize of comparable area, wherever the latter is planted. This is the case whether there are host-plants in the crop or not. By contrast, when a maize Bt11/MON 810 field has no margins, then a single block of non-Bt-maize is slightly more effective than sown strips at reducing mortality of NT lepidopteran larvae.
For NT lepidopteran species of conservation concern occurring within protected habitats, it is appropriate for thresholds used to derive recommendations for risk management to be based on a criterion of local mortality; for NT lepidopteran larvae occurring within maize fields and their margins a criterion of global mortality is considered appropriate.
Seed mixtures (e.g., refugia in a bag) provide the poorest possible efficacy of mitigation because they do little to limit the exposure of non-target Lepidoptera to Bt-maize pollen.
In general, for any particular Bt-maize plant expressing Cry1 protein, the required isolation distance around protected habitats within which sources of maize Bt11/MON 810 pollen should not be cultivated increases with: (a) the sensitivity of the NT lepidopteran larvae and (b) the expression levels of the Cry1-protein in Bt-maize pollen. In the present case of maize Bt11/MON 810, it is confirmed that imposing an isolation distance of 20 m around a protected habitat from the nearest crop of maize Bt11/MON 810 would be expected to reduce local mortality, even of extremely highly sensitive non-target lepidopteran larvae, to a level at or below 0.5%. This estimated isolation distance is conservative, since it assumes extremely high levels of sensitivity in NT lepidopteran larvae, and because larvae within the habitat will be at greater distances from the Bt-maize crop than those on the edge of the habitat.
The EFSA GMO Panel considers that the potential of regionally occurring non-target lepidopteran pests to evolve resistance exists but is considerably less than that of target pests and therefore routine IRM would not be proportionate. Hence, the EFSA GMO Panel reiterates that regionally occurring non-target lepidopteran pests should be considered within the PMEM. General surveillance shall be used to report information on unexpected larval damage to maize and observations on the occurrence and survival of lepidopteran larvae on Bt-maize plants. In addition, monitoring reports from regional plant inspection services should be used to trigger subsequent investigations, including CSM if necessary. The applicants should amend their PMEM plans accordingly.
This Scientific Opinion provides background scientific information to inform the decision-making processes; the EFSA GMO Panel reiterates that risk managers should choose risk mitigation and management measures that are proportionate to the level of identified risk according to the protection goals pertaining to their regions.
Bt11, Cry1Ab, environmental safety, GMO, insect resistance, maize (Zea mays), mathematical modelling, MON 810, non-target Lepidoptera