Sublethal pesticide effects, synergistic interactions and resilience strategies in honey bees (Apis mellifera): A narrative review.

Pesticide exposure at chronic, field-realistic doses represents a major driver of honey bee colony weakening through sublethal and synergistic effects. This narrative review synthesizes evidence from 2010 to 2025 on neurophysiological, immunological, and behavioral impacts of major insecticide classes, with emphasis on pesticide-fungicide synergies largely ignored by regulatory risk assessments anchored to acute LD₅₀ endpoints. We discuss the Sublethal Toxicity Ratio (SubTR) as a heuristic indicator of sublethal potency and highlight critical knowledge gaps: sublethal effect data are absent for most registered pesticides, and the toxicity of over 99% of potential pesticide mixtures remains untested. Current mitigation strategies, including probiotic supplementation and nutritional support, show promising laboratory results but lack large-scale field validation. We propose a conceptual framework integrating sublethal hazard, synergistic potential, and mitigation effectiveness to prioritize future research. A paradigm shift toward chronic, mixture-based, colony-level testing is urgently needed alongside Integrated Pest Management and floral resource restoration to safeguard pollinator health.