Assessment of the 2023 post-market environmental monitoring report on the cultivation of genetically modified maize MON 810 in the EU

At the request of the European Commission, the European Food Safety Authority (EFSA) assessed the 2023 post-market environmental monitoring (PMEM) report on the cultivation of the genetically modified maize event MON 810, which expresses the Cry1Ab protein. The report provides no evidence of adverse effects from maize MON 810 cultivation. It confirms high refuge compliance among farmers in Spain and Portugal. However, uncertainty remains on compliance in areas where clustered maize MON 810 fields exceed five hectares. No signs of practical resistance to Cry1Ab were found in corn borer populations sampled in north-eastern Spain in 2023, although reduced susceptibility in Mediterranean corn borer populations from this area cannot be excluded. Information collected through farmer questionnaires in Spain and scientific literature searches revealed no unanticipated adverse effects on human and animal health, or on the environment. However, EFSA remains concerned about the potential exposure of non-target lepidopteran species classified as ‘very highly’ or ‘extremely’ susceptible to Cry1Ab to harmful amounts of maize MON 810 pollen. Several recommendations from previous PMEM report assessments remain unaddressed and new shortcomings were identified. Particularly, EFSA emphasises the urgent need to: (1) increase the sensitivity of the insect resistance monitoring strategy; (2) implement mitigation measures to ensure exposure of non-target lepidoptera to maize MON 810 pollen remains at levels of no concern; (3) harmonise farmer questionnaires across Spain and Portugal; and (4) revise the remedial action plan. Finally, EFSA acknowledges the proactive initiatives undertaken by the Competent Authorities of Spain in support of the PMEM activities and encourages continued collaboration to strengthen monitoring and risk management measures.