The European Food Safety Authority (EFSA) has concluded that the 2024 post-market environmental monitoring (PMEM) report on the cultivation of genetically modified maize MON 810 provides no evidence of unexpected adverse effects on human and animal health or the environment, but it warns that reduced susceptibility to the Cry1Ab protein in Mediterranean corn borer (MCB) populations from north-eastern Spain cannot be excluded. In a statement published on 3 August 2026, EFSA also identified methodological shortcomings in both case-specific monitoring and general surveillance, and recommended streamlining general surveillance to focus on a strengthened farmer complaint system and transparent annual literature searches.
The assessment, prepared at the request of the European Commission's Directorate-General for Health and Food Safety, reviewed the 2024 PMEM report covering insect resistance management and general surveillance. EFSA noted that refuge compliance was generally high in Spain (96.8% of farmers cultivating more than 5 hectares reported implementing a refuge) and fully achieved in Portugal, but uncertainty remains where clusters of small MON 810 fields may collectively exceed the 5-hectare threshold. The authority reiterated the importance of full compliance, particularly in high-adoption areas, and welcomed efforts by the Spanish Competent Authorities to identify such clusters and strengthen farmer awareness.
On resistance monitoring, EFSA found that corrected moult inhibition values for European corn borer (ECB) were in line with the expected >99% threshold, but MCB values remained below the threshold in all three populations tested in 2024, continuing a pattern observed since 2022. Combined with unexpected field damage reported in Girona in 2021 and indications of resistance alleles detected in 2024, EFSA stated that reduced Cry1Ab susceptibility in MCB populations cannot be excluded. The authority reiterated the need to increase monitoring sensitivity, for instance through periodic F2 screens, and welcomed the applicant's confirmation that F2 screens will replace annual diagnostic assays for MCB populations from 2025 onwards, starting with Girona. However, EFSA maintained that ECB populations should also be subjected to resistance allele frequency estimation.
EFSA also highlighted persistent concerns in Girona, where monitoring data from 2022 to 2024 show low susceptibility, and considered the follow-up actions implemented in 2024 insufficient. The authority called for strengthened resistance monitoring and communication in the area, including targeted field scouting and efforts to select a resistant MCB population for further characterisation.
Regarding general surveillance, EFSA noted that farmer questionnaires in Spain and annual literature searches did not identify unanticipated adverse effects, but it flagged limitations in the questionnaire's scope and representativeness, and noted that Portuguese data remain less informative. The farmer complaint system was seen as a useful complement but its current design does not yet allow EFSA to assess its effectiveness. EFSA also identified uncertainties about the potential exposure of highly sensitive non-target Lepidoptera to MON 810 pollen in protected habitats, due to a lack of implementation data on isolation distances.
After more than two decades of cultivation without evidence of unexpected adverse environmental effects, EFSA proposed streamlining general surveillance to two core elements: a strengthened farmer complaint system, complemented where appropriate by existing plant health and pest monitoring networks, and transparent, comprehensive annual literature searches. The authority welcomed ongoing research on teosinte hybridisation and fitness in Spain and France, and encouraged continued data exchange and monitoring.
The statement was approved on 8 July 2026 and authored by EFSA staff including Antoine Messéan, Yann Devos, Fernando Álvarez, and Ana M. Camargo. EFSA's conclusions will inform the European Commission's ongoing review of MON 810 cultivation conditions, with potential implications for farmers in Spain and Portugal, the main cultivation areas, as well as for the consent holder and national competent authorities responsible for monitoring and risk management.