Novel strategy with an eco-friendly polyurethane system to improve rainfastness of tea saponin for highly efficient rice blast control

Improving rainfastness of agro-chemicals on leaves to reduce chemical leaching onto the ecosystem and aerosol drift is a huge challenge in modern agriculture and environmental protection. In this study, tea saponin (TS), a natural product and efficient bio-pesticide, was blended with environmentally-friendly vegetable oil-based waterborne polyurethanes. The chemical structures, mechanical properties, thermal stability, slow-release behavior of the composite films with different TS contents and the inhibitory effect of composites on mycelia growth of rice blast were studied. It is found that the release rate of TS from the composite films could be tailored by controlling the TS content of the composite emulsion. The composites prepared exhibit excellent inhibitory effect on the mycelia growth of rice blast, even after rainfall washing. This is the first time that bio-based and degradable polymer films with sustained-release of TS are proposed to control rice blast diseases with enhanced rainfastness.