Sea urchin-like nanocarrier for enhancing pesticide retention and rain fastness on hydrophobic and hydrophilic crop foliage

Foliar washoff by rainfall is a major factor inducing the inefficient utilization of pesticides. Enhancing the adhesion and retention of pesticide on plant foliage has long been of interest. The presence of waxy platelets on most plant foliage surfaces renders them rough and hydrophobic. This reduces the area of contact between pesticide particle and plant foliage, which decreases the adhesion. In this study, we developed a pesticide nanocarrier (PANI/HACC) with sea urchin-like surface morphology based on polyaniline (PANI) doped with biodegradable 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC). Then, azoxystrobin (AZOX) loaded nanoparticles (AZOX@PANI/HACC) was synthesized by physical adsorption. It exhibited retention rates of 61.4% on rice leaves and 64.6% on cucumber leaves, which were higher than that of commercially available azoxystrobin water dispersible granules (AZOX-WDG, 42.1% and 24.5%, respectively) and suspension concentrates (AZOX-SC, 23.1% and 58.8%, respectively). Additionally, pot experiments demonstrated that the control efficacy of AZOX@PANI/HACC on rice against Rhizoctonia solani was 1.64-fold and 3.0-fold of that of AZOX-WDG and AZOX-SC, respectively. The higher retention performance of AZOX@PANI/HACC was attributed to the stable adhesion by fitting nanometer-sized spikes into the spaces between the waxy platelets. Overall, the pesticide nanocarrier with spiky surface morphology provides an effective strategy for improving pesticide retention and reducing pesticide loss in agricultural production.