Efficacy of Melia azedarach leaf extract in different solvents against Heterotermes indicola Wasmann (Blattodea: Rhinotermitidae) using non-durable wooden blocks under laboratory and field conditions

Abstract

Hetertermes indicola Wasman (Blattodea: Rhinotermitidae) is a highly wood-destructive termite species in the urban settings of Pakistan. This study evaluated the biocidal action of Melia azedarach leaf extract in different solvents on H. indicola by conducting choice and no-choice feeding deterrence assays using impregnated palatable wood under field and laboratory conditions. Dose-dependent and time-dependent trends were observed in the leaf extracts of M. azedarach at different concentrations (500, 1000, and 1500 ppm) using solvent water and methanol with 80–100 % termite mortality after 6 days of exposure. A key outcome was the higher termiticidal efficacy of methanolic extract compared to aqueous extract under both field and laboratory conditions. The LC50 values of 358 ppm for methanol and 466 ppm for aqueous extract after 15 days in a laboratory no-choice experiment exhibit a quantitative measure of chinaberry leaf extract toxicity. A significant reduction in mean percent weight loss (8.26 %) of treated wood with 1500 ppm of M. azedarach leaf extract in methanol was observed under field conditions. In conclusion, triterpenoids and phytol present in methanolic leaf extract demonstrated higher efficacy in both lab and field conditions making a solid foundation for the further development of natural wood preservatives. Since they induced rapid lethargic conditions in termites and digestive toxicity which leads to minimum loss of treated wood.