Combined Control of Rice Sheath Blight Using a Biobased Pickering Emulsion Co-Formulated with Two Pesticides

Abstract Rice sheath blight, a globally significant disease caused by Rhizoctonia solani (R. solani), can be effectively managed through a codelivery technology that combines the action of two pesticides. This approach, which involves multitargeted, coordinated intervention against the pathogen, enhances the efficacy of pesticides and reduces the required dosage. Therefore, this study employed electrostatic self-assembly to prepare chitosan-alkali lignin (AC) nanocomposite particles as stabilizers. Through systematic optimization of oil–water ratio and ultrasonic power, a novel dual-drug Pickering emulsion delivery system (AZO@ACVA) was successfully constructed for combined efficacy control of rice sheath blight. This system achieves efficient coloading of the hydrophilic pesticide validamycin (VA) and the hydrophobic pesticide azoxystrobin (AZO), demonstrating multiple functional advantages: within the acidic microenvironment formed by pathogen infection, the carrier exhibits pH-responsive release properties, enabling intelligent combined efficacy release of both drugs. On leaf surfaces, the amphiphilic structure of the AC nanocarrier combined with the combined efficacy effect of Tween 80 significantly enhances the wetting and adhesion of the emulsion on both hydrophobic rice leaves and hydrophilic cucumber leaves. The deposition levels reached 2.28 times and 1.89 times that of commercial formulations, respectively, with markedly improved resistance to rain wash-off. Simultaneously, the combined efficacy barrier effect between the lipid phase and lignin effectively delays the photodegradation of pesticides. Antimicrobial experiments demonstrate significant combined efficacy effects between VA and AZO in this system, resulting in a substantially higher inhibition rate against rice sheath blight pathogens compared to either commercial pesticide alone. Furthermore, this fully biomass-based system substantially reduces acute toxicity to zebrafish, exhibiting excellent environmental compatibility. This study presents a biobased Pickering emulsion platform for the codelivery of hydrophilic and hydrophobic pesticides, providing a green and efficient strategy for controlling rice sheath blight with reduced environmental impact.