Chitosan-based nanoparticles of avermectin to control pine wood nematodes

Pine wood nematode disease is a most devastating disease of pine trees. Avermectin (AVM) is a widely used bio-nematocide which can effectively to kill the pine wood nematode (PWN). However, its poor solubility in water and rapid photolysis are responsible for its poor bioavailability, which causes environmental pollution because of excessive applied rates. Here, a simple electrostatic interaction method was used to encapsulate AVM within nanoparticles composed of poly-γ-glutamic acid (γ-PGA) and chitosan (CS). The loading capacity of the resulting AVM-CS/γ-PGA nanoparticles was as much as 30.5%. The encapsulation of AVM within these nanoparticles reduced its losses by more than 20.0% through photolysis. An in vitro test showed that the rate of release of AVM from the nanoparticles was dependent on the ambient pH, with rapid release occurring in an alkaline environment. The mortality rate of nematodes which were treated with 1ppm of AVM content of AVM-CS/γ-PGA was 98.6% after 24h, while one of free AVM was only 69.9%. In addition, FITC-labeled CS/γ-PGA nanoparticles (FITC-CS/γ-PGA) showed that the nanoparticles could enrich in intestines and head of nematodes. All of these results showed that those nanoparticles of AVM are a potential multifunctional formulation to control the pest and reduce environment pollution.