Effect of Khaya senegalensis and Trichilia emetica Plant Extracts against Sweet Potato Weevil (Cylas puncticollis Boheman)

Abstract

Introduction: Sweet potato weevil (Cylas punticollis) is a pest of economic importance with negative impacts on sweet potato production. Due to the hazardous nature of insecticides, deploying plant extracts against this pest is an eco-friendly alternative. Aim: This study aimed to evaluate the potential of extracts of Khaya and Trichilia plants for antifeedant activity and toxicity against adult C. punticollis. Methodology: In this study, the leaves and barks of Khaya senegalensis and Trichilia emetica plants were tested for antifeedant activity and toxicity against adult C. punticollis at 2.5ppm, 5ppm, 10ppm, 20ppm and 40ppm through the No-choice bioassay method. Ethanol and aqueous solvents served as negative checks, and Lara force as a positive check. An independent sample t-test was used to analyze the differences between the feeding holes on the treated strip and the feeding holes on the control strip. Tukey’s multiple test was used to assess the differences in antifeedant rates of the two botanicals and different concentrations. Results with p < 0.05 were considered significant. Results: The results revealed that Lara force caused the strongest feeding deterrence against C. punticollis. Among the plant extracts, the highest (56.23%) and the lowest (11.73%) percentage of feeding punctures were observed in the ethanolic and aqueous extracts of the leaves of T. emetica, respectively. However, the antifeedant potency of the plant extracts treated potato slips did not significantly differ from the control slips after 24 hours of weevil exposure to potato slips. The mortality of C. punticollis was dependent on the concentration of the extracts and the duration of exposure to the plant extracts. The highest percentage of mortality (90%) was recorded at 40 ppm among the plant extracts. The order of toxicity among the treatments includes 40 ppm > 20 ppm > positive check > 10 ppm > 5 ppm > 2.5 ppm > negative control. Conclusion: Overall, this study accentuates the potential of extracts from Khaya and Trichilia plants and their application in managing sweet potato weevil.