Effect of Grevillea robusta leaf extract in comparison with synthetic phytol on Heterotermes indicola Wasmann (Blattodea: Rhinotermitidae) and its gut flagellates

Heterotermes indicola (Blattodea: Rhinotermitidae) is the major wooden structural pest throughout the world except Antarctica. Pakistan is one of the foremost home of H. indicola having highly favorable environment. In the present study, phytol a synthetic commercial compound was experimented for its termiticidal activity along with its synergistic effect with Grevillea robusta ethanolic leaves extract. G. robusta leaves were shade dried and their ethanolic extract was prepared via Soxhlet apparatus. Five bioassays were setup to evaluate termiticidal and protozoacidal effects of Phytol (10, 20, 30, 40, 50, 100 and 150 ppm) and G. robusta leaf extract (100, 500, 1000, 1500 and 2000 ppm). Synergism of Phytol (50 ppm) and G. robusta (2000 ppm) along with Repellency and antifeedant activity of Phytol (10, 20, 30, 40, 50, 100 and 150 ppm) were also evaluated. Later on synergistic response of G. robusta and phytol on non-durable wood was experimented. After force feeding the termite workers with filter paper and wood treated with various concentrations of phytol and G. robusta leaf extract for 15 days, there was a significant decline in the population of gut protozoa. A dose dependent mortality and foraging response was observed when H. indicola was force-fed on phytol and G. robusta leaf extract. At 100% mortality was recored maximum concentration (150 ppm) of phytol and 77% mortality was recorded at maximum concentration (2000 ppm) of leaf extract. Both phytol and G. robusta leaf extract showed significant decline in the population of gut protozoa where phytol caused 88% and leaf extract caused 60% reduction of hindgut protozoa count as compared to control groups (P < 0.001). Phytol also showed repellent and antifeedant activities against H. indicola. Synergistic effect of silver oak leaf extract and phytol was also observed which showed 96% termite mortality and 86% reduction in gut protozoa, which was significantly higher than the effects produced by either treatment alone. Phytol and leaf extract were also separately and synergistically tested on non-durable woods. In these assays H. indicola showed significant mortality (100%), confirming potential termiticidal activity of both agents (P < 0.001) and decline in hindgut protozoa (92%) in all the treated groups (Phytol, leaf extract and synergism.