Potency of Methanol Extract of Some Botanicals as Contact Insecticide against Two Termite Species

Abstract

Termites, hemimetabolous insects of the order Isoptera are mainly endogenic and constitute a nuisance to agricultural production. Conventionally, termites have been managed with the use of synthetic insecticides which have been shown to pose serious adverse effects to humans and the environment. There is, therefore, the need to explore alternative methods with less environmental hostile effects. To this end, this work was aimed at evaluating the effectiveness of three plant extracts for termites’ control in order to reduce farmers’ dependence on synthetic chemicals. Contact activity of methanol extract of leaves from three botanicals (Ageratum conyzoides, Tephrosia vogelii, and Alternanthera sessilis) were assessed against two termite species. One syringe drop of different concentrations of each extract (1.5 mL, 3.0 mL, and 4.5 mL) was applied on the dorsal part of each termite in a Petri dish, and mortality was observed at 30, 60, 90, and 120 mins, and 12 hours after treatment. The experiment was a 12 × 2 factorial in Completely Randomized Design (CRD) with three replications. Phytochemical components of the plant materials were determined using standard procedures. Results showed that 4.5 mL Tephrosia vogelii  had a  significantly (p < 0.05) faster and higher contact toxicity effect on the termite species, followed by 4.5 mL Ageratum conyzoides and 4.5 mL Alternanthera sessilis. However, the toxicity of 3.0 mL T. vogelii and A. conyzoides was comparable with the synthetic insecticide. Correlation and GGE biplot analysis revealed that flavonoids were the main phytochemical determinant of T. vogelii and A. conyzoides contact activity.