A biodegradable water-triggered chitosan/hydroxypropyl methylcellulose pesticide mulch film for sustained control of Phytophthora sojae in soybean (Glycine max L. Merr.)

Phytophthora root rot (PRR) caused by Phytophthora sojae (P. sojae) is one of the serious diseases that affect soybean production. Presently, there are some problems such as threatening the environment and human health in main methods of controlling PRR. Herein, a natural polymer composite mulch film with water-triggered pesticide release prepared for the sustained control of PRR was firstly reported. 5 different mulch films were obtained by blending different proportions of chitosan (CS) and hydroxypropyl methylcellulose (HPMC), and the metalaxyl (Me) was then loaded in the mulch films. The proper mulch film (Me-CS50/HPMC50) was selected by the assessments of tensile property, water solubility and light transmittance, and the formation mechanism and micromorphology of Me-CS50/HPMC50 were furthering characterized. To reveal the application prospect of the Me-CS50/HPMC50 in the management of PRR, some physical and biological properties were evaluated. The pesticide release rate of Me-CS50/HPMC50 within 72 h was 70.6%, while CK was 97.3%. Besides, the in vitro antifungal and pot experiments showed that the Me-CS50/HPMC50 could against the P. sojae and the incidence rate of PRR was only 13.3%. This work can provide a new research idea, which has potential application to effectively control PRR and develop sustainable agriculture.