Leaf adhesion and insecticidal efficacy of a starch-chitosan based dual-network hydrogel pesticide delivery system

Constructing functionalized hydrogel carrier materials for controlled release pesticide delivery to improve foliar adhesiveness and photostability is of great significance for increasing pesticide utilization rates and reducing residue pollution. In this study, a novel dual-network hydrogel, CST-CS-TA-Zn²⁺, functionalized with tannic acid (TA) and zinc ions (Zn²⁺) using cassava starch (CST) and chitosan (CS), was fabricated via a semi-dissolved acidified sol-gel method combined with response surface optimization strategy. Furthermore, a composite hydrogel pesticide delivery system incorporating acetamiprid (ACE), named ACE@CST-CS-TA-Zn²⁺, was prepared via physical adsorption. The ACE@CST-CS-TA-Zn²⁺demonstrated robust foliar adhesion on banana leaves, pH-responsive release, and markedly enhanced photostability-retaining 24.72% more active ingredient than technical ACE, with 58.24% of the loaded ACE remaining after 30 h of UV-vis irradiation. Bioassays against cowpea aphids revealed significantly enhanced insecticidal efficacy, evidenced by LC₅₀ values of 2.49 mg a.i. L^-1 (24 h) and 0.85 mg a.i. L^-1 (48 h), representing 3.4- and 3.2-fold reductions relative to technical grade ACE. The non-target toxicity assessment result demonstrated a trend of lower toxicity risk for bees. The findings establish a design strategy and experimental foundation for developing sustainable multifunctional composite hydrogels tailored for controlled release pesticide delivery.