Novel Biodegradable Composite Mulch Film Embedded with Temperature-Responsive Pesticide Microcapsules for Durable Control of Phytophthora Root Rot on Soybean

Soil-borne diseases have caused substantial economic losses to agricultural production due to their rapid onset and few means of control. Here, pyraclostrobin (Pyr) microcapsules (Pyr@MCC) with temperature-responsive pesticide release capability were prepared using temperature-sensitive phase-change materials as capsule cores. Then, the Pyr@MCC was organically combined with poly(vinyl alcohol)-starch film (PVA/ST) to prepare a composite mulch film (PM/PVA/ST) with intelligent control of pesticide release rate according to external temperature change, which realized sustainable and efficient control of Phytophthora root rot (PRR) on soybean. Tensile tests showed that the PM/PVA/ST film exhibited good tensile deformation ability (134.9%) and high tensile stress (18.0 Mpa). The water vapor transmission rate test showed that the PM/PVA/ST film exhibited good barrier performance to H2O, CO2, and O2. The release test data proved that the PM/PVA/ST film could slowly release Pyr at lower temperatures (15 °C) and release Pyr rapidly at higher temperatures (35 °C), corresponding to the high temperature at which the Phytophthora root rot outbreak. In vitro antifungal and pot experiments showed that the PM/PVA/ST film had a good control efficiency on Fusarium spp. These results show that the functional pesticide microcapsules loaded onto the film have good application potential for controlling PRR on soybean. In general, this composite mulch film provided some innovative research ideas for optimizing the pesticide delivery pathway and thereby efficiently controlling soil-borne pests and diseases, reducing the frequency and amount of pesticide use and minimizing white pollution from traditional plastic mulch films.