New strategy for improving the rainfastness and control effect on Monochamus alternatus of clothianidin via a castor oil-based polyurethane nanoemulsion

Pine wilt disease (PWD) is one of the most destructive diseases affecting global forest ecosystems, and Monochamus alternatus (MA) is the main insect vector of pine wood nematodes. Effective control methods that cover the entire emergence period of vector insects are urgently required. Improving the rainfastness of agrochemicals on leaves can extend the holding period. Thus, a new environmentally friendly castor oil-based polyurethane nanoemulsion (CWPU-NE) was developed to enhance the rainfastness of clothianidin. CWPU adsorbs on the surface of clothianidin particles through electrostatic and intermolecular hydrogen bonding and attaches to the surface of leaves through hydrogen bonding and film formation. The results showed that clothianidin was still effective against MA 60 d after application. The developed CWPU-NE functioned as an efficient rainfastness adjuvant that enhanced the rainfastness, retention, protection, and sustained release behavior of clothianidin. Thus, it has great potential for PWD control and wider agricultural applications.