Rain‐fast octylamine–dopamine‐grafted alginate film controls wheat powdery mildew and halves triadimefon usage

Abstract BACKGROUND Fungicide resistance in Blumeria graminis f. sp. tritici and on‐target deposition below 30% undermine wheat powdery mildew control. A durable, rain‐fast foliar film that intercepts early infection can synergize with fungicides to reduce chemical inputs and environmental loss. This study therefore developed and assessed a dual‐functional alginate coating that combines hydrophobic anchoring with mussel‐mimetic adhesion to extend leaf coverage, restrict the pathogen and reduce triadimefon use. RESULTS Octylamine and dopamine were grafted onto sodium alginate to produce a self‐filming coating (SDO). At ≥0.2% (w/v) SDO covered >75% of the leaf surface and significantly reduced conidial germination and colony formation. In pot assays, 0.2% SDO alone provided >55% protective and curative efficacy. Formulating half‐dose triadimefon (100 mg L –1 ) in 0.2% SDO (Tri@SDO) raised control to 78.8% (protective) and 87.7% (curative), matching the full commercial dose. After simulated rainfall, Tri@SDO retained 72.3% efficacy versus 57.8% for the fungicide alone. Seed germination exceeded 96%, and no phytotoxic effects were detected in seedlings. CONCLUSION The dual‐functional alginate coating forms a persistent physical barrier and synergises with triadimefon, providing full disease control with 50% less fungicide and superior rainfastness. This approach offers a practical means to mitigate fungicide resistance and environmental dissipation, advancing sustainable management of wheat powdery mildew. © 2026 Society of Chemical Industry.