Sustained Release of Azoxystrobin from Clay Carriers for the Management of Maize Late Wilt Disease

Controlled-release technologies based on natural clays represent a promising strategy for enhancing the efficacy, sustainability, and environmental compatibility of agrochemicals. Here, we present a comprehensive study on the development and characterization of clay-based azoxystrobin (Az) formulations designed to control Magnaporthiopsis maydis , the causal agent of maize late wilt disease. Among the six tested carriers, two (raw bentonite and raw sepiolite) were selected for their similar adsorption capacity and simplicity of preparation. A novel mycelial plug-immersion bioassay was developed and optimized to evaluate release dynamics and antifungal activity with superior sensitivity and resolution compared to conventional disk-diffusion or mycelial growth-inhibition assays. Sequential wash experiments and extended incubation assays revealed sustained Az release equivalent to ≥ 1 mg L⁻¹ over 144 hours, resulting in strong fungal growth suppression. A comparative analysis of particle suspensions and supernatants revealed formulation-specific release behaviors, likely linked to the mineral structure and surface properties. These findings highlight the capacity of bentonite and sepiolite to act as efficient carriers that prolong fungicide bioavailability, reduce leaching, and maintain biological efficacy. They provide proof of concept for clay–Az systems as sustainable and cost-effective tools for LWD management. Beyond their immediate application in plant disease control, the results advance fundamental understanding of clay–active ingredient interactions and offer a versatile platform for the design of controlled-release systems in agricultural and environmental contexts.