ROS‐Responsive and ‐Regulated Polysaccharide‐Based Nanodelivery System Enabling Phloem‐Targeted Fungicide Delivery for Apple Vascular Disease Control

Abstract Apple tree canker, a persistent threat to economically valuable apple trees, poses a serious challenge to the global apple industry. The phloem colonization property of pathogen Valsa. mali makes traditional control strategies ineffective in delivering fungicides to vascular tissue and controlling the infection. Developing a phloem‐mediated fungicide nanodelivery system to achieve inward‐to‐outward control of apple tree canker represents a highly promising strategy. Herein, an innovative reactive oxygen species (ROS)‐responsive starch‐based tebuconazole nanodelivery system (Teb@PT‐CMS) inspired by the interaction mechanism between pathogen and host plant is successfully constructed. Teb@PT‐CMS, with an average size of 107.8 nm, exhibits a dose‐dependent release of tebuconazole in response to H 2 O 2 stimulation and is successfully absorbed through apple leaves, achieving systemic distribution via the phloem pathway. Bioactivity tests show that Teb@PT‐CMS enhances disease prevention efficacy by up to 2.4 times over conventional formulations (22.4% ± 3.4%) and reduces ROS levels in plant tissues by enhancing antioxidant enzyme activity. Additionally, the PT‐CMS nanocarriers significantly reduce tebuconazole toxicity in human HepG2 cells and do not induce excessive plant defense responses even at high concentrations. This groundbreaking external pathogen prevention and internal oxidative regulation strategy offers a transformative approach to precisely control vascular diseases and promote sustainable agricultural practices.