STUDIES ON ACTIVITIES AND CONTROL OF TERMITES IN THREE AGROECOLOGIES IN NIGERIA

Abstract

Termites are serious cosmopolitan pests of wooden and earthen materials in most parts of the world especially in the tropics. This study centred on the survey of termite activities for damage assessment in and around buildings in twenty selected towns in four States of Nigeria namely Ondo, Ekiti, Kogi and Federal Capital Territory spanning three agroecologies of swamp forest, rainforest and savannah. The bioinsecticidal potential of seventeen plants were assessed and wood preservation potential of three plant oils on termites was determined in graveyard for 12 weeks using standard techniques. Cypermethrin (2.5g/L) and untreated control were also used to surface-treat the woods. The toxicological and histopathological effects of the most potent bioactive plant were investigated using standard histological techniques and enzyme markers. The study was designed to study the potential toxic effects of A. difformis on the liver and kidney of Wistar rats by using various biochemical indices and histopathology. The rats were divided into five groups (I–V) and were treated as follows: group I (negative control); groups II, III, and IV had 1, 2.5 and 5% of A. difformis respectively included in their diets; and group V (positive control) had 5% permethrin in their diets. The experimental treatment lasted 30 days after which the animals were sacrificed, and the blood collected for the determination of serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), urea and creatinine. The liver and kidney were excised for histopathological and biochemical analyses. All experiments were performed in replicates. Data obtained was subjected to analysis of variance and the significant means were separated by the New Duncan's Multiple Range Test. Where necessary lethal dose (LD50) and lethal time (LT50) were determined to ascertain the lethal doses and the lethal time for 50% of the experimental animals. The survey revealed the termite activities in 1094 buildings (54.7%) of 2000 inspected buildings. Residents found termites most commonly around the buildings in piles of plant branches while termites were commonly found inside the buildings on the walls. Residents noticed termite activity mostly through damaged woods (52.22%), followed by mud tube construction (24.02%), then termite wing or body (13.72%), termite mounds (10.04%) and termite faecal pellets (0%). Termites were abundant and mostly distributed in rainforest compared to other agroecological zones. Twenty termite species were collected and identified in the three agroecological zones. Macrotermes subyalinus Silvestri, was the most prevalent (15.80%) termite species found around the building premises while dry wood termite Neotermes nigeriensis (Sjostedt) was least abundant (0.52%) in the buildings. Cubitermes severus was not found in the swamp forest. Evaluation of twenty plant extracts as wood protectants, the oils of Jatropha curcas and Jatropha gossipifolia, rhizome extract of Anchomanes difformis and leaf extract of Nicotiana tabacum have effective wood preservative potential against termites. Anchomanes difformis was the most toxic and effective of all the plant extracts evaluated. The log-probit analysis revealed that A. difformis had the least mean LD50 and LT50 in all the treatments of 4.51%w/v at 24 h post treatment and LT50 of 18.65 h at 2.5%w/v plant extract concentration. The results suggest that mortality increased with increase in concentration and exposure time. Phytochemical test revealed that A. difformis rhizome contains alkaloids, saponins, tannins, resins and flavonoids. The toxicological results showed that serum levels of AST, ALT, ALP, urea, and creatinine were significantly higher (P ˂ 0.05) in rats that were maintained on diets that contained 5% A. difformis and 5% permethrin compared to those maintained on basal diets, 1 or 2.5% A. difformis. On the other hand, the liver and kidney levels of AST, ALT, ALP, urea, and creatinine were significantly lower in rats that were maintained on diets that contained 5% A. difformis and 5% permethrin compared to those maintained on basal diets, 1 or 2.5% A. difformis. Also, maintenance of rats on diets that contained 5% A. difformis and 5% permethrin resulted in apparent damage to the liver and kidney. This study has shown the level of safety of A. difformis on mammals; it is both hepatotoxic and nephrotoxic at high levels; therefore, caution must be applied when using the plant as herbal medicine. It is suggested that A. difformis powder should not be used at high concentration to protect wood and crop meant for consumption.