In its 2011 Scientific Opinion updating the evaluation of the environmental risk assessment and risk management recommendations on the genetically modified (GM) insect resistant maize 1507 for cultivation, the EFSA GMO Panel recalibrated the mathematical model, developed by Perry et al. (2010), in order to simulate and assess potential adverse effects resulting from the exposure of non-target Lepidoptera (butterflies and moths) to pollen from maize 1507 under representative EU cultivation conditions, and extended it to estimate the efficacy of certain risk mitigation measures. The EFSA GMO Panel concluded that risk mitigation measures may be needed under specific conditions (depending on, for example, sensitivity and occurrence of non-target Lepidoptera, acreage of Bt-maize, host-plant density) in order to reduce the exposure of sensitive non-target (NT) Lepidoptera to maize 1507 pollen. 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 Cry1F 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 additional information on the factors affecting the IRM plan, additional to that in its 2011 Scientific Opinion on maize 1507. 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 maize 1507 pollen, there is a potential hazard to non-target lepidopteran larvae on their host-plants in fields cropped with non-Lepidoptera-active crops when they neighbour the maize 1507 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 1507 has no margins containing host-plants of non-target lepidopteran larvae, the only larvae exposed are those on any host-plants within the GM crop. When such host-plants are present, a greater percentage of the larvae exposed to maize 1507 pollen are expected to suffer mortality than when a field has margins with host-plants. This is the case despite the fact that fewer individual larvae are expected to suffer mortality (because there are fewer individual larvae exposed).
If a maize 1507 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 1507 field has no margins, then a single block of non-Bt-maize is slightly more effective than sown strips.
For non-target 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 non-target lepidopteran larvae occurring within maize fields and their margins a criterion of global mortality is considered appropriate.
Spatial arrangements of non-Bt-maize should always be placed to maximise the average distance of non-target lepidopteran larvae from the nearest source of maize 1507 pollen. Consequently, seed mixtures provide the poorest possible efficacy of mitigation and do little to limit the exposure of non-target Lepidoptera to Bt-maize pollen.
In general, for any particular GM Bt-maize plant expressing Cry1 protein, the required isolation distance around protected habitats within which sources of Bt-maize pollen should not be cultivated increases with both the sensitivity of the NT lepidopteran larvae and the expression levels of the Cry1-protein in Bt-maize pollen. In the present case of maize 1507, it is confirmed that imposing an isolation distance of 30 m around a protected habitat from the nearest crop of maize 1507 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 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 reiterates that regionally occurring lepidopteran pests should be considered within the post-market environmental monitoring (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 plant inspection services should be used to trigger subsequent investigations, including case-specific monitoring if necessary. The applicant should amend its PMEM plan accordingly.
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.