Harnessing essential oil synergy to enhance the repellency of partially biobased polymer against sap-feeding hemipteran pests

Sap-feeding hemipteran pests, such as aphids, cause significant yield losses and remain difficult to control sustainably, as conventional insecticides face increasing limitations due to resistance development and growing concern over human and environmental health. Plant essential oils (EOs) constitute a promising, eco-friendly alternative. However, their large-scale application is constrained by poor field stability and high production costs. These limitations may be mitigated through improved formulation and efficacy optimization, therefore reducing the amount of EO required for effective pest management. In this study, we investigated the repellent activity of binary and ternary blends of basil ( Ocimum basilicum L.), Chinese cinnamon ( Cinnamomum cassia (L.) J. Presl), and spearmint ( Mentha spicata L.) EOs, incorporated into a polybutylene succinate co-adipate (PBSA) biopolymer matrix, against the pea aphid Acyrthosiphon pisum Harris. Applying a conceptual framework derived from mixture toxicology, we found that both the M. spicata–O. basilicum binary blend and the ternary combination exhibited strong synergistic interactions, resulting in an 8- to 24-fold increase in repellent potency compared to individual oils. Further exploration of different M. spicata–O. basilicum ratios led to additional improvements in blend efficiency. When tested on other sap-feeding hemipteran species, this optimized blend also demonstrated interspecific repellency. Our results support the rational design of EO-based bio-repellent blends as sustainable tools for pest management. • Essential oil (EO)-PBSA polymer films were tested as repellents for the pea aphid. • Some EO blends showed strong synergistic effects. • Synergistic blends greatly reduce the amount of EO needed for effective repellency. • The optimized 3:7 spearmint-basil blend exhibited efficacy across hemipteran pests. • Results support the rational design of EO-based bio-repellents for pest management.