Metal-phenolic coated and prochloraz-loaded calcium carbonate carriers with pH responsiveness for environmentally-safe fungicide delivery

The study of release mechanisms of pesticides with respect to environmental and biological factors facilitates improvement in pesticide use efficiencies and reduction in environmental risk. In this study, prochloraz (Pro), a highly effective fungicide, was loaded into starch-doped porous calcium carbonate (CaCO 3 ), which was subsequently coated with a metal–phenolic film to prepare a pH-responsive delivery system (PC@TA/Cu). Results demonstrated that CaCO 3 had a mean diameter of 1.55 µm and its loading capacity for Pro was ~15.2%. PC@TA/Cu microparticles show good adhesion to rapeseed oil leaves and resisted washout with simulated rainwater. The cumulative release rate of PC@TA/Cu particles at pH = 3 was 1.63 times higher than that in near-neutral pH environment for 48 h. This pH-responsive release characteristic could be associated with the oxalic acid secreted by Sclerotinia sclerotiorum . The control effect against Sclerotinia disease with 100 μg/mL of Pro content of PC@TA/Cu was 56.8% after 7 d, while that of Pro EW (emulsion in water) was 45.8%. Finally, biosafety tests showed a 4-fold reduction in the acute toxicity of PC@TA/Cu to zebrafish, compared to the that of Pro technical. The carrier (CaCO 3 @TA/Cu) had no significant effect on the growth of rapeseed oil seedlings. The results showed that the prepared PC@TA/Cu has long-lasting disease control capability and significantly reduced toxicity to non-target organisms, making it valuable for potential applications.