A high-efficiency nano-fungicide recruits the beneficial microorganisms against destructive pepper southern blight (Sclerotium rolfsii)

Nanopesticides have a promising prospect in actual production due to their small size, excellent wettability and superior bioactivity, but their potential impacts on environmental health remain critical knowledge gaps. Herein, we applied star polycation (SPc) to successfully construct an efficient nano-fungicide pyraclostrobin (PYR)@SPc. The SPc spontaneously assembled with PYR through hydrogen bonding and Van der Waals forces, forming stable spherical particles with nanoscale size (102 nm). The complexation with SPc decreased the contact angle of PYR, increased its retention, and enhanced leaf wettability. Importantly, the SPc significantly increased the direct fungicidal activity of PYR by effectively inhibiting the activity of mitochondrial complex III and decreasing ATP content in Sclerotium rolfsii . The PYR@SPc exhibited excellent fungicidal activity against destructive pepper southern blight in greenhouse and field trials, with the increase in control efficacy by 1.6-2.06 times. Moreover, the extended persistence of PYR efficacy also contributed to the sustainable management of diseases. Interestingly, microbiome analysis indicated that the PYR@SPc altered the structure and diversity of microbial communities in soil, reorganized soil microbial networks, aggregated keystone taxa, and improved soil disease resistance and degradation functions. Compared to PYR alone, the application of PYR@SPc significantly increased the abundances of Sphingomonas (13.86%) and Bacillus (11.61%), and the enriched B. siamensis strain S27 could be isolated to control pepper southern blight. Overall, these findings demonstrated that the SPc could not only improve the direct fungicidal activity of PYR against S. rolfsii , but also recruit the beneficial microorganisms in the rhizosphere for synergistic control of fungal diseases.