A <scp>pH</scp> ‐responsive vanillin‐Schiff base microcapsule for controlled release of pyraclostrobin

Abstract BACKGROUND Environmentally responsive microcapsules hold great promise for sustainable pest management by improving efficacy, lowering dosage and enhancing environmental compatibility. Herein, a pH‐responsive pyraclostrobin (Pyr)‐loaded microcapsule (Pyr@PU) with an isocyanate core and vanillin‐Schiff base polyurethane shell were successfully fabricated via interfacial polymerization. RESULTS The obtained microcapsules exhibited high loading capacity (80.89%) and encapsulation efficiency (96.17%), indicating excellent drug loading and encapsulation performance. In vitro release experiments confirmed that the Pyr@PU microcapsules exhibited prominent pH‐responsive release behavior, with a higher cumulative Pyr release (82.81%) at pH 4.0 after 144 h. Meanwhile, the prepared Pyr@PU microcapsules possessed excellent photostability, favorable leaf wettability and superior rainfastness. Bioactivity assays revealed that the microcapsules exerted favorable antifungal effects. At 200 μg mL −1 , Pyr@PU provided protective and curative efficacy of 79.62% and 67.59% against kiwifruit pathogens, as well as 57.90% and 37.89% on rice leaves, respectively. Biosafety evaluation showed that Pyr@PU reduced the 96‐h acute toxicity to zebrafish by 2.3‐fold and displayed no obvious adverse effects on rice seed germination. CONCLUSION The fabricated pH‐responsive Pyr@PU microcapsule exhibits superior UV resistance, leaf adhesion, rainfastness, antifungal efficacy, and biocompatibility. As a promising intelligent controlled‐release platform for pesticides, Pyr@PU provides both control efficacy and environmental compatibility, showing great potential for application in sustainable agriculture. © 2026 Society of Chemical Industry.