Effects of teak, Tectona grandis Linn, heartwood extractives against Heterotermes indicola (Isoptera; Rhinotermitidae)
B Hassan, S Ahmed, M Mankowski, G Kirker, R E Ibach, M Misbah ul Haq
Heartwood extractives from Tectona grandis were investigated for antitermitic activities against Heterotermes indicola in laboratory experiments. Extractives were removed from wood shavings by soxhlet extraction using an ethanol: toluene (2:1) solvent system. Termite feeding and mortality followed a concentration dependent response. The highest termite mortality occurred at an extractive concentration of 10 mg/ml. The calculated LC50 based on the concentration dependant response was 3.2 mg/ml. Extractives showed high repellency and antifeedant activity against H. indicola. Tests in which extractives were used to vacuum-pressure treat southern pine and cottonwood, showed that T. grandis extractives imparted resistance to these non-durable species. At the highest concentration of extractives tested, complete mortality was observed after termites were exposed to extractive-treated southern pine and cottonwood. Compared to solvent controls, minimum weight losses of 3.6 and 3.5% were observed for extractive-treated southern pine and cottonwood, respectively, at the 10mg/ml concentration after 28 days of exposure. Termites exposed to a subset of extractive treated then leached southern pine and cottonwood showed high mortality. These results suggest that T. grandis extractives have antitermitic properties and may be potentially useful in the development of environmentally friendly wood preservative.