Selective Wax Cuticle Removal Using Green Wavelength Lasers: A Non-Invasive Method for Enhancing Foliar Uptake

A laser-based selective wax ablation method using a 532 nm Nd:YAG laser was developed to improve the foliar uptake efficiency of agrochemicals in citrus leaves. In contrast to conventional applications that suffer major losses, our approach exposes up to 80% of the underlying epidermis (within the irradiated footprint) with no visible tissue damage, thereby substantially enhancing substance penetration. Efficacy was confirmed using two indicators: (1) A fluorescent glucose analog (2-NBDG) exhibited a radial expansion velocity reaching 0.0105 mm/min in treated areas, enabling rapid phloem transport across an 8 cm distance within just three minutes—an 11,280% improvement over untreated controls. (2) Laser-induced breakdown spectroscopy (LIBS) demonstrated a threefold increase in zinc (Zn) uptake (and over fivefold compared to untreated leaves) when using a Zn-based foliar fertilizer. To assess processing efficiency, we quantified the ablation footprint by combining single-pulse laser shots in a 1 cm-diameter region and found that 23.4% of the total area was fully exposed. This selective, non-invasive approach enables precise targeting, potentially reducing fertilizer and pesticide usage while improving crop health. Beyond citrus, it is readily adaptable to other crops, with integration into orchard or greenhouse spraying systems as a promising path for scale-up. Such versatility highlights the technique’s potential to optimize efficacy, cut input costs, and diminish environmental impact in modern precision agriculture.