Phytochemical Screening and Evaluation of Insecticidal Effect of Hydro-Ethanolic Extracts of Leaves and Bark of Nauclea latifolia (Rubiaceae) on Workers of Macrotermes bellicosus (Rambur, Isoptera) in the Laboratory

Abstract

Pesticides are increasingly criticized for their harmful effects on the environment and the health of farmers by environmental protection organizations and farmers themselves. Faced with this, new strategies including the use of plant-based extracts are proposed. The objective of this study is to evaluate the insecticidal effect of two plant extracts on Macrotermes bellicosus workers. Thus, through phytochemical screening and direct toxicity test, the secondary compounds and the insecticidal effect of hydro-ethanolic extracts of the bark and leaves of Nauclea latifolia were respectively evaluated. Phytochemical screening revealed the presence of sterols, polyphenols, saponins, flavonoids and alkaloids in the hydro-ethanolic extracts of the bark and leaves of N. latifolia. On the other hand, it revealed an absence of tannins in both extracts. The direct toxicity test showed the efficacy of both extracts on M. bellicosus workers. The LD 50 of the hydro-ethanolic extract of the bark of N. latifolia (49.5 mg/L) was 2.6 times lower than that of the hydro-ethanolic extract of the leaves (129.55 mg/L). Total mortality with the hydro-ethanolic extract of the bark with doses of 50 and 100 μl was obtained 72 hours after treatment, while with the hydro-ethanolic extract of the leaves, it was obtained 96 hours after treatment. Efficacy is raised with the hydro-ethanolic extract of the bark. The consumption test revealed the presence of veneer in both treated and control samples. Filter papers were consumed for both extracts in both treated and control samples extracts of the bark and leaves of N. latifolia are effective against M. bellicosus workers. They can be recommended for the control of termite pests after evaluation of their acute toxicity to mammals.