Interfacial Engineering of Fatty Alcohol Polyoxyethylene Ether Enables Lesion-Targeted Deposition on Pathogen-Infected Apple Leaves

Pathogen infection creates heterogeneous, rough leaf interfaces that hinder pesticide deposition at disease lesions. Here, we report an interfacial engineering strategy using fatty alcohol polyoxyethylene ether surfactants (AEO-4 to AEO-7) to achieve selective deposition on apple Alternaria blotch lesions. Through interfacial characterization (surface free energy, roughness, contact angle), high-speed droplet impact analysis, and energy dissipation modeling, we systematically evaluated the structure–activity relationship of AEO surfactants. Field validation was conducted under natural disease conditions to assess control efficacy and spray volume reduction. Infection induced a Cassie–Baxter wetting barrier on lesions due to increased roughness ( S q up to 39.3 μm) and chemical heterogeneity. AEO-4 at 0.05 wt% (≥5 × CMC) optimally reduced surface tension to 27.12 mN·m –1, suppressed droplet rebound, and promoted selective retention via surface tension reduction, micellar permeation, and topological locking. The energy dissipation rate on lesions reached 72.4%, yielding 3.2-fold higher deposition than pure water. Field trials demonstrated that 0.05 wt% AEO-4 enabled 35.5% reduction in spray volume and 52.93% reduction in active ingredient while maintaining ∼85% control efficacy equivalent to high-concentration treatments.