Dual-coated emamectin benzoate nano-formulation with enhanced systemic translocation and insecticidal activity based on lignin/urea-formaldehyde.

To enhance pesticide utilization efficiency and environmental safety, this study developed a dual-coated emamectin benzoate sustained-release nano-formulation (EB@Lignin-C14/UF) using lignin tetradecanoate (Lignin-C14) and urea-formaldehyde resin (UF) as carriers. Through esterification modification to improve lignin hydrophobicity as the inner layer and UF cross-linked network as the outer barrier, the uniform spherical nanoparticles with average size of 95.5 nm were prepared via high-speed stirring-ultrasonic dispersion. Thermogravimetric analysis demonstrated enhanced thermal stability. The dual-coated system showed 24-h release of 37.34 ± 1.24 % in 40 % methanol-water, representing 13.5 % and 26.9 % reductions compared to single-carrier (43.17 ± 1.58 %) and microemulsion (51.06 ± 2.39 %), respectively. Through dual physical barrier and chemical protection mechanisms, the formulation reduced photodegradation rate by 25.5 % (0.38 %/h vs 0.51 %/h for microemulsion). Biosafety assessments indicated 15-30 % reduction in rice germination inhibition and significantly lower ecotoxicity to zebrafish compared to conventional microemulsion. Pot experiments demonstrated prolonged insecticidal duration to Spodoptera litura with 58.7 ± 3.33 % efficacy at 25 days post-application, showing 24 % and 1.6-fold improvements over single-coated (34.67 ± 0.22 %) and EB microemulsion (22.67 ± 0.44 %). This natural-synthetic polymer dual-coated synergy provides an innovative solution to challenges including pesticide burst release, photodegradation, and eco-toxicity, offering both theoretical foundation and technical reference for designing green pesticide formulations.