Evaluation of Antitermite Properties of Wood Extracts from Pongamia pinnata (L.) Pierre (Leguminosae) against Subterranean Termites

Termiticide, repellent and antifeedant activities of extracts from Pongamia pinnata wood were evaluated against Coptotermes heimi (Wasmann) at three different concentrations preceded by a preliminary choice and no-choice tests for natural resistance of tested wood. Termites' mortality was determined in each case of extract and solvent treated Whatman filter paper. Finally, wooden blocks of poplar (19×19×19 mm) were treated with extracts and respective solvents and exposed to termites in the field for 28 days. Minimum mean weight loss was observed in dried P. pinnata (6.38%), followed by fresh P. pinnata in choice tests. In no-choice tests, dried P. pinnata was comparatively resistant with a weight loss of 12.37%, followed by fresh P. pinnata and P. deltoides. In toxicity bioassay, ethyl acetate-based wood extracts caused the highest mortality (41.66%), followed by petroleum ether, hexane, and water extracts at 10 mg/ml concentration. Similarly, ethyl acetate-based extracts showed maximum repellency (100%) followed by petroleum ether extracts at 10 mg/ml and ethyl acetate at 5 mg/ml after 60 min of termite exposure. Minimum wood losses were observed in woods treated with ethyl acetate extracts compared to control and other treatments in field experiments.