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

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.

Synergism of three botanical termiticides as wood protectants against subterranean termites, Macrotermes subhyalinus (Rambur, 1842)

“…Some were however harvested from surface termite tunnels at night when they forage for food as well as infested logs of wood. The harvested termites in the study area had earlier been identified as Macrotermes subhyalinus (Rambur) in a study conducted by Ajayi et al (2018). Dark chambers were constructed using the method of Ali, Ahmed, Sheridan, and French (2016) with some modifications.…”

“…Aqueous extracts of each plant material used in this study were prepared according to the method of Ajayi et al (2018) with little modifications. Powders of each of the three plant parts weighing 10 g were properly admixed together in dual (ratio 1:1) and tricombinations (ratio 1:1:1).…”

“…The profile of compounds in the botanical mixture of the plant parts was evaluated using the method of Ajayi et al (2018) with little modifications. The phytochemical constituents of the dual (A. indica + N. tabacum and N. tabacum + J. curcas) and tri-combinations (A. indica + N. tabacum + J. curcas) of powders of the three plant parts was done using head space-solid-phase microextraction, gas chromatography-mass spectrometry (HS-SPME, GC-MS) analysis.…”

“…In sub-Sahara Africa, Macrotermes subhyalinus (Rambur) is one of the commonest and most damaging termite species in agro-forestry areas (Pearce, 1997). This species of African subterranean termite has been reported in Nigeria by Ajayi (2012) as well as Ajayi, Adedara, and Oyeniyi (2018). M. subhyalinus was reported to be capable of causing total destruction of crops and wooden structures within few months under favorable climatic conditions due to their voracious feeding behavior (Malaka, 1996;Nyeko & Olubayo, 2005).…”

“…Several plants species have therefore been investigated for their anti-termite potentials under laboratory and field conditions. Most of the plants were observed to exhibit toxic, repellent, and antifeedant properties against several species of termite (Acda, 2014;Ajayi et al, 2018;Osipitan, Jegede, Adekanmbi, & Ogunbanwo, 2013;Raina, Bedoukian, Florane, & Lax, 2012). For instance, Azadirachta indica (A.…”