Surfactants, cellulose nanocrystals, and chitosan: Their contributions to pesticide delivery systems

Improving pesticide utilization efficiency is vital for environmental sustainability, economic growth, and the protection of human and animal health, particularly in water-based formulations. Numerous studies have shown that surfactants can enhance pesticide encapsulation and improve deposition efficiency on plant surfaces. This review examines the roles of surfactants in pesticide formulations from the perspective of their structural classifications, including conventional, gemini, trimeric, and polymeric surfactants, with a particular focus on how molecular structure influences the droplet behavior and delivery performance. We highlight the applications and functional roles of sustainable, biodegradable, and renewable biomaterials, specifically cellulose nanocrystals (CNC), chitosan, and their derivatives, in foliage- and soil-applied pesticide delivery systems. While both CNC and chitosan possess excellent carrier properties, attaining high deposition efficiency on plant surfaces continues to be a significant challenge. Combining the biomaterials with surfactants offers an effective strategy to improve pesticide utilization. Additionally, this review outlines the current understanding of droplet dynamics on hydrophobic and superhydrophobic plant surfaces, highlighting the mechanisms and formulation strategies used to control droplet behavior and enhance deposition. Finally, we outline key challenges and future directions for the development of next-generation pesticides that integrate high efficacy, reduced environmental impact, and long-term sustainability, thereby advancing the future of eco-friendly crop protection systems.