ASSESSMENT OF INDIGENOUS PRESERVATIVES ON THE RESISTANCE OF ISOBERLINIA DOKA (Craib & Stapt) AND TRIPLOCHITON SCLEROXYLON (K. Schum) TO TERMITES IN NORTH-WESTERN NIGERIA

Abstract

Wood protections against the attack of wood bio-degradation agents have being in practice over the years. Some locally available preservatives have also being in use without ascertaining their efficacies. An assessment of some selected indigenous preservatives was carried out using preliminary survey and field trial experiment in the North-western Nigeria. The preliminary survey study was carried out to generate information on indigenous methods of wood preservation and treatment while field experiment was carried out to investigate the effect of Solignum and two identified commonly used preservatives in the studied areas. Extracts of Euphorbia balsamifera (Aguwa) and Sabulun-salo (mixture of millet residue + groundnut oil) were tested against termites on Isoberlinia doka (Doka) and Triplochiton scleroxylon (Obeche) wood species. Defect free samples of Obeche and Doka species were selected, prepared according to ASTMD 334-74 standards. Non-pressure method (cold-dipping) was used in applying the preservatives. The treatment combination consisted of four treatments i.e. two local bio-insecticides Aguwa (LBI-I) and Sabulun-salo extract (LBI-II), one conventional insecticide (Solignum) and a control replicated five times and laid out in randomized complete block design (RCBD). The wood samples were exposed to termite attack to test the efficacy of the preservative treatments on the wood species in Sokoto, Kebbi and Kano States from North-western zone of Nigeria. The preliminary survey data was analyzed using descriptive statistics while field experiment data were analyzed using analysis of variance (ANOVA) at 5% probability level. The results of preliminary survey of indigenous methods of wood preservations showed that 21.7, 18.6 and 19.6% of Sokoto, Kebbi and Kano States respondent respectively use Solignum mixed with spent engine oil, just as 10, 8.0 and 12.1% of Sokoto, Kebbi and Kano States respectively suggested the use of Aguwa extract and 7.1% and 5.0% of Kebbi and Kano state respectively suggested the use of Sabulun- salo extract. The results also showed that the use of Diesel mix with gamalin40 which was just 1.7, 2.2 and 1.7% in Sokoto, Kebbi and Kano State respectively was found to be practically lower than the other method of wood preservation. The results of field experiment showed that there were significant differences between the two species (i.e. Doka and Obeche) P<0.05 and preservatives treatment. Density of the selected wood species was determined and classified into high and low density class with Doka having the higher density than Obeche and Obeche absorbs more preservatives than Doka. Termite identified at the study location was subterranean termite (Coptotermes formosanus) in all the three locations. Weekly visual observations of the stakes carried out as specified in ASTM D3345-80 Standards for 48 weeks. Solignum and Aguwa extract has the lowest percentage weight loss of 9.4 and 15.6% respectively while the control sample has the highest percentage weight loss of 49.5% on Obeche. On the other hand, Doka Solignum and Aguwa extract has the lowest percentage weight loss of 8.1 and 13.4% respectively. The control samples have the highest percentage weight loss of 56.2%. These results indicated that Solignum and Aguwa treated samples provided better protection against subterranean termite (Coptotermes formosanus) compared with Sabulun-salo treated samples for the 48 weeks testing period. It can therefore be concluded that Aguwa extract proved effective in the protection of Isoberlinia doka (Doka) and Triplochiton scleroxylon (Obeche) against termite attack.