Termiticidal efficacy of extracts of two indigenous plants against Macrotermes subhyalinus Rambur (Blattodea: Termitidae)

Ajayi, O. E., Adedara, W. and Oyeniyi, E. A

NJE Vol. 34: 109-122, 2018

DOI: 10.36108/NJE/8102/43(0121)

Abstract: The termiticidal potentials of methanol, n-hexane, acetone and water extracts of heart wood of Milicia excelsa (Welw.) C. Berg and leaves of Khaya senegalensis (Desr) and their botanical mixture against Macrotermes subhyalinus (Rambur) attacking Triplochiton scleroxylon (Obeche) wood blocks were evaluated in this study. The trial lasted for 12 weeks in open field and under shade conditions. Visual rating and weight loss determination were used to assess the level of termite damage on treated wood blocks. Treated wood blocks in the open field were comparatively less infested than those under shade. Botanical mixture extracted with n-hexane protected the wood blocks better than all of methanol, acetone and aqueous extracts. Also, treated wood blocks in open fields had lower percentage weight loss to termite compared to those under shade. The GC-MS analysis revealed the presence of thirty-four and fourty-four compounds in M. excelsa and K. senegalensis, respectively. Milicia excelsa, however, contains more toxic compounds [Butylated Hydroxyl toluene (BHT), Docosane, Tridecane, Cyclohexane and Citra] than K. senegalensis (Cyclohexane and Cucubene). Milicia excelsa could, therefore, be touted as a better wood protectant than K. senegalensis, especially in the open field. The mixture of n-hexane extract of both plants was more potent at protecting the wood blocks for three months duration. Various insecticidal compounds identified in each plant could also be adopted as eco-friendly termiticidal agents for managing subterranean termites.
Keywords: Milicia excelsa, Khaya senegalensis, Triplochiton scleroxylon, weight loss.

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