Crop leaves naturally exhibit a curved morphology and primarily display bending deformation and vibrational responses under wind load. The curved surface structure of leaves plays a critical role in the deposition and retention of pesticide droplets. In this study, wind tunnel experiments combined with high-speed photography and digital image analysis were conducted to systematically investigate the curvature and flexibility distributions of three typical crop leaves: walnut, peach, and pepper, across a range of wind speeds. The results indicate that with increasing wind speed, all three types of leaves gradually transition from smooth, uniform bending to a multi-peak pattern of pronounced local curvature, with increasingly prominent nonlinear deformation characteristics. Moreover, once the wind speed exceeds the critical threshold of 6 m/s, the primary deformation region generally shifts from the leaf base to the tip. For example, the maximum curvature of walnut leaves increased from 0.018 mm⁻¹ to 0.047 mm⁻¹, and that of pepper leaves from 0.031 mm⁻¹ to 0.101 mm⁻¹, both more than double their original values. In addition, all three types of leaves demonstrated a distinct structural gradient characterized by strong basal rigidity and high apical flexibility. The tip flexibility values exceeded 1.5 × 10⁻⁵, 4 × 10⁻⁴, and 5.6 × 10⁻⁴ mm⁻²·mN⁻¹ for walnut, peach, and pepper leaves, respectively. These findings elucidate the mechanical response mechanisms of non-uniform flexible crop leaves under wind-induced bending and provide a theoretical basis and data support for the optimization of air-assisted spraying parameters.

Conventional spraying often results in poor deposition on the abaxial (lower) leaf surface and within the middle-to-lower canopy, where pest and disease pressures are typically highest. In this study, we evaluated the performance of electrostatic spraying using basil (Ocimum basilicum), cucumber (Cucumis sativus), and chili pepper (Capsicum annuum) leaves as target surfaces. A high-speed imaging system was employed to map droplet distributions on the abaxial surface, while a neighborhood-matching algorithm combined with droplet tracking was used to quantify the motion of individual droplets near the leaf. At the steady-state stage (frame 4500, 2.25 s), the number of charged droplets detected beneath the abaxial surface increased by 112% (basil), 132% (cucumber), and 213% (chili pepper) compared with non-electrostatic spraying. Smaller charged droplets exhibited higher horizontal velocities and smaller deflection angles in their trajectories near the leaf, indicating a stronger tendency to migrate toward the target surface and into the canopy interior. These findings demonstrate that electrostatic forces substantially enhance abaxial deposition and provide practical guidance for optimizing parameters for electrostatic spraying, such as droplet size, to improve spray efficiency in agricultural applications.