A Rapid pH-Responsive Pyraclostrobin Delivery System with Enhanced Membrane Passing Property and Fungicidal Activity against Botrytis cinerea

Abstract

As the second most important fungal pathogen, Botrytis cinerea (B. cinerea) poses a serious threat to crop yields and agricultural safety. Pyraclostrobin (PYR), a broad-spectrum QoI fungicide, has been widely utilized since its launch in 2003. However, the inhibitory effects of both PYR technical and PYR formulations on B. cinerea are not outstanding. Even at a concentration of 50 μg/mL, the inhibition rates of B. cinerea by both PYR technical and PYR formulations remain below 85%. In this work, we prepared an acid-responsive Pickering emulsion encapsulating PYR (PYR@BTIB-PE), which completely inhibited B. cinerea at low concentrations (25 μg/mL) for the first time. The PYR@BTIB-PE achieved fragmentation and release within 4 min at pH 5, which was consistent with the pH around B. cinerea. The PYR@BTIB-PE can rapidly release PYR when B. cinerea infected and increased the concentration of PYR around the B. cinerea, thereby enhancing the efficacy of PYR. In addition, the released organic solvent from PYR@BTIB-PE enhanced the passing property of the B. cinerea membrane, facilitating more PYR to enter the body of B. cinerea. The improvement of the membrane passing property and rapid response release of PYR@BTIB-PE worked together to achieve complete inhibition of B. cinerea. Furthermore, the flexible and amphiphilic structures of PYR@BTIB-PE increased its interaction with the leaf surface, completely suppressed droplet splashing, and promoted droplet spreading, thereby reducing pesticide loss and improving the utilization rate of the pesticide. This study presents an efficient and rapid strategy for inhibiting B. cinerea and is also expected to be extended to other antifungal preparations.