Phytochemical Screening and Insecticidal Effects of Some Botanical Powders against Periplaneta americana in Otukpo, Benue State, Nigeria

Abstract

This study evaluated the phytochemical composition and insecticidal efficacy of six selected botanical powders against the American cockroach, Periplaneta americana, in Otukpo, Benue State, Nigeria. The botanicals investigated were Azadirachta indica, Terminalia catappa, Cymbopogon citratus, Citrus sinensis, Carica papaya and Prunus dulcis. Laboratory bioassays were conducted using graded concentrations of plant powders mixed with biscuit bait, and mortality was recorded at 24, 48 and 72 hours. Phytochemical screening revealed that all tested plants contained biologically active secondary metabolites, including steroids, phenols, flavonoids, glycosides, alkaloids and saponins, with Azadirachta indica exhibiting the highest abundance of these compounds. Descriptive statistics were used to analyse mortality counts, while probit regression analysis was used to calculate LC values at a 5% significance level (p≤0.05). The results showed a time-dependent increase in mortality across treatments, with longer exposure periods resulting in increased insect death. Azadirachta indica demonstrated the highest insecticidal activity, achieving up to 95.8% mortality after 72 hours and recording the lowest LC₅₀ (0.12 g) and LC₉₅ (1.45 g), indicating strong toxicity. Citrus sinensis and Carica papaya showed moderate to high effectiveness, while Cymbopogon citratus exhibited moderate activity. In contrast, Prunus dulcis and Terminalia catappa showed relatively low insecticidal effects. Overall, the order of efficacy was A. indica > C. sinensis > C. papaya > C. citratus > P. dulcis > T. catappa. The findings suggest that botanical powders, particularly neem, have potential as eco-friendly alternatives to synthetic insecticides for managing P. americana in domestic environments. However, further validation using standardised extraction methods and improved statistical modelling is recommended.