Dual action of the innovative thymol-based green bioformulation in storage: control of pest insects and improvement of seed quality

Developing sustainable strategies for the protection of stored legumes is essential due to the extensive damage caused by the dried bean beetle ( Acanthoscelides obtectus ). In this study, an innovative green bioformulation based on thymol loaded into cellulose acetate beads (CAB-T) using supercritical CO 2 was tested, aiming to achieve prolonged release of the active compound and provide dual biological action: protection of bean seeds from insect damage and enhancement of seed physiological quality during long-term storage. Material characterization confirmed efficient thymol loading (∼26 wt%) and revealed slight pore narrowing combined with weak polymer–thymol interactions, indicating successful incorporation into the matrix. Thymol release from CAB-T exhibited markedly reduced volatilization compared to neat thymol, with only ∼58% released after 40 days in air, demonstrating effective gradual-release performance. Insecticidal assays demonstrated a strong and concentration-dependent effect of CAB-T on adult mortality, reduction in longevity, and complete inhibition of progeny production at concentrations of ≥20 mg (equivalent to 5.12 mg thymol). CAB-T also displayed high repellency (80–88%, class V) across a broad concentration range, whereas neat thymol showed only moderate repellence and rapid loss of activity. Beyond pest control, CAB-T significantly improved bean seed quality after 90 days of treatment. Seed germination, root and shoot growth, seedling dry mass, and vigor indices increased substantially, indicating a strong biostimulatory effect. • Cellulose acetate beads impregnated with thymol (CAB-T) have a long-lasting effect. • CAB-T showed high repellency and insecticidal effect on dried been beetle. • CAB-T displayed biostimulatory effect on common bean seed. • CAB-T is an innovative and perspective pest control material in storage condition.