Abstract:
Anacardium occidentale (L.) shell oil, Jatropha curcas (L.) and Ricinus communis (L.) seed oils were extracted using n-hexane and tested as wood protectant against subterranean termites using Triplochiton scleroxylon (Schumann) as wood substrate in vitro at 25, 50, 75, and 100% concentration levels for each of the oils. The oils were also mixed at ratios 1:1 and applied at 25, 50, 75 and 100 % (v/v) to test possible synergistic effect of the oils for wood protection against subterranean termites. Negative controls (untreated and solvent-treated wood samples) and positive control (Diazinon treated wood samples), and an experiment to determine weight loss due to environmental factors were included. All treatments were replicated 3 times. Experiments were arranged on termites infested field, and observed for signs of termite infestation weekly for a period of 14 weeks. Visual observations were rated using America Standard for Testing Materials(ASTM, 1991). The difference between initial and final weight of wood samples at 14th week of exposure to termites was used as index of protectant-ability of the plant oils. All oils significantly (P<0.05) protected the wood but the degree of effectiveness varied with increased concentrations and plant species from which the oils were extracted.A. occidentale shell oil was the most effective of all the three oils with weight loss range between0.49 and 6.60% while the least was R. communis oil with weight loss range between3.04 and 31.29%. All the mixtures showed synergistic effect as they were more effective than each of the oils when used singly. The effectiveness of single oils at 100% and mixtures of the oils at 25% v/v compares favourably with effectiveness of the standard chemical used as positive control. No antagonistic effect was observed in all the mixtures tested. The results of this study suggest anti-feedant or repellent properties in the oils.
