Toxicity and repellency of chlorpyrifos nanocapsules against subterranean termite Coptotermes curvignathus

Chlorpyrifos is widely used in agricultural and building industries to control many insects including termites. However, its low aqueous solubility and tendency to decompose under sunlight results in decrease in its efficiency. In the present study, chlorpyrifos was encapsulated into nano-sized poly (styrene-co-maleic anhydrite) using a mini-emulsion in-situ polymerization method to improve the effective utilization rate. The termiticidal properties of nanocapsules at different concentrations (1 - 25 wt%) were tested against subterranean termite; Coptotermes curvignathus. Results of Choice bioassays shows that chlorpyrifos nanocapsules are strongly toxic to Coptotermes curvignathus. The filter paper feeding inhibition and repellent bioassay show a significant feeding inhibition (> 60 %) at lowest concentration of chlorpyrifos nanocapsules. The highest mortality rate of termites (90 %) after 24-h exposure was observed in the sample treated with the highest concentration of chlorpyrifos nanocapsules (25 wt%). Results obtained from this study show that chlorpyrifos nanocapsules have a strong termiticidal property against Coptotermes curvignathus. This indicates that the nanoencapsulation of biocides chlorpyrifos opens a real potential of new and advanced wood preservation technology.