Scientific assessment of the 2024 post-market environmental monitoring report on the cultivation of genetically modified maize MON 810 in the EU.

At the request of the European Commission, EFSA assessed the 2024 post-market environmental monitoring (PMEM) report on the cultivation of genetically modified maize MON 810, which expresses the Cry1Ab protein. Using a weight-of-evidence approach and considering information provided by the consent holder and the Competent Authorities of Portugal and Spain, EFSA concluded that the PMEM report provides no evidence of unexpected adverse effects on human and animal health, or on the environment associated with the cultivation of maize MON 810 in 2024. Refuge compliance was generally high in Spain and fully achieved in Portugal. However, uncertainty remains in situations where clusters of small maize MON 810 fields may collectively exceed the 5-ha threshold requiring refuge implementation. No evidence of practical resistance to Cry1Ab was identified in European corn borer populations sampled in north-eastern Spain in 2024. Nevertheless, the consistently low Cry1Ab susceptibility observed in Mediterranean corn borer populations from this area between 2022 and 2024, together with unexpected field damage reported in Girona in 2021 as well as indications of resistance alleles detected in 2024, indicate that a decrease in susceptibility cannot be excluded. EFSA also considers that the current resistance monitoring strategy lacks sufficient sensitivity for the early detection of resistance evolution. General surveillance activities, including farmer questionnaires in Spain and annual literature searches, did not identify unanticipated adverse effects. However, uncertainty remains regarding the potential exposure of highly sensitive non-target Lepidoptera to maize MON 810 pollen due to the lack of implementation data on isolation distances toward protected habitats. EFSA also identified methodological and reporting shortcomings in both case-specific monitoring and general surveillance, while welcoming the continued efforts of the Competent Authorities of Spain to address data gaps and support refinement of monitoring and risk management measures. After more than two decades of cultivation without evidence of unexpected adverse environmental effects, EFSA considers that general surveillance could be streamlined to focus on two core elements: (1) a strengthened farmer complaint system, complemented where appropriate by existing plant health and pest monitoring networks; and (2) transparent and comprehensive annual literature searches.