ABSTRACT

The effectiveness of cashew nut (Anacardium occidental# L.) shell liquid (CNSL), incision density and age in protecting Gmelina arborea Roxb. wood against subterranean termite attack was investigated. Gmelina wood stakes from two age series (5 and 10 years) of gmelina plantations were incised at five incision densities (0/m2, 300/m2, 600/m2, 900/m2and 1200/m2) and treated with five CNSL concentrations (0%, 3%, 6%, 9% and 12%) before being subjected to 12 months (January to December) field evaluation in three locations (Uyo, Abak and Itu) of high termite incidence in Akwa Ibom State of Nigeria. The second component of this study consisted of the investigation on: the effect of solvent type on the yield of CNSL extraction, determination of the most suitable concentration of CNSL (diluted with ethanol) and incision density for effective treatment of gmelina wood against subterranean termite damage, determinations of physiocochemical properties of CNSL from Uyo cashew plantation and some physicochemical properties of gmelina wood samples used in the study using standard analytical methods and effect of incision density on drying, wood movement (shrinkage and swelling) and treatability (retention and penetration) of gmelina wood with CNSL preservative . The results indicated that the combined effect of CNSL preservative and incision density had a significant influence in protecting gmelina wood against subterranean termites with incision densities of 600/m2 at 9% CNSL concentration and 900/m2 at 9% CNSL concentration being the most economical treatment combination that gave 100% (termite damage rating of 10) protection of gmelina wood against subterranean termites for 5 years and 10 years treated stakes respectively. N-hexane with least CNSL extraction time of 240 minutes, mean CNSL yield of 5.11g, anacardic acid, cardanol and cadol yields of 58.90g, 18.96g and 9.50g respectively and 5.33, 42.5 and 0.926 yields respectively of pH, viscosity and specific gravity proved best among the evaluated solvents (n-hexane, ethanol and methanol). Physicochemical properties of CNSL from cashew plantation in Uyo were comparable to international standards for CNSL. Incising significantly reduced the drying time and significantly increased drying rate of gmelina wood. The best incision density for drying time and drying rate of 5 and 10 years old gmelina wood was 900/m2.' Incision density did not have any significant effect on shrinkage and swelling of gmelina wood. Age of gmelina tree had a significant effect on shrinkage and swelling of gmelina wood with 10 years old gmelina wood having significantly higher percent shrinkage and swelling than their 5 years old. Shrinkage and swelling also varied significantly with tree height (stem section) in both ages. Combined effect of incision density and CNSL concentration was significant in increasing the retention and penetration of CNSL in treated stakes in 5 and 10 years old gmelina wood with 600/m2 incision density and 9% CNSL concentration and 900/m2 incision density and 9% CNSL concentration being the economically best treatment combinations for 5 and 10 years old wood respectively. Age of gmelina wood samples significantly affected its retention and penetration with 5 years old wood having higher retention and penetration than 10 years old. Significant variation in moisture content with gmelina stem section with moisture increasing from base to top of tree also existed in both ages. Significant variation in density with stem section with density decreasing from base to top existed in 10 years old gmelina wood but not in 5 years old. Investigation to establish the shelve life of CNSL preservative is suggested. To treat gmelina wood against termites, the use ofCNSL is highly desirable.