Sustainable treatment of banana leaves for phytosanitary applications: impact, spreading, and impregnation of mineral oil

BACKGROUND Efficient application of phytosanitary sprays is essential for sustainable control of foliar fungal diseases such as Black Sigatoka in banana crops. Mineral oils are commonly used for their fungistatic properties, yet their modes‐of‐action, particularly their interactions with leaf tissues, remain poorly understood. This study aims to elucidate the physical behavior of mineral oil droplets on banana leaves and their subsequent diffusion into internal tissues. RESULTS High‐speed imaging shows that mineral oil droplets reach their maximum spread without retraction and exhibit only low splashing at high impact velocities. Spray coverage is strongly anisotropic and increases over time following a power‐law scaling ( t a with α = 0.21 ± 0.02), in agreement with Tanner's law. Micro‐infrared spectroscopy reveals that mineral oil penetrates the leaf, with preferential accumulation in the palisade parenchyma. Diffusion into internal leaf tissues, specifically the palisade parenchyma, follows Fick's law after a latency of ≈3.6 h, with an effective diffusion coefficient of (1.2 ± 0.8) × 10 −8 cm 2 s −1 . CONCLUSION This study provides the first direct evidence that mineral oils not only protect leaf surfaces, but also diffuse into internal tissues targeted by fungal pathogens. These findings offer a mechanistic basis for field practices and support the development of more effective and sustainable foliar spray formulations.