Phytochemical Screening and Bio-Insecticidal Efficacy of Alligator Pepper (Aframomum melegueta), Pepper Fruit (Dennettia tripetala), and Guinea Cubeb (Piper guineense) Seed Powder on Cockroaches (Blattella germanica; Order: Blattodea, Family: Ectobiidae)

Abstract

A laboratory investigation was conducted to assess the efficacy of seed powders derived from Alligator pepper [Aframomum melegueta], Pepper fruit [Dennettia tripetala] and Guinea cubeb [Piper guineense] in managing German cockroach [Blattella germanica] nymphs. Different concentrations (0.0, 10, 20, 30, and 40% w/v) of the seed powders were topically applied to the dorsal surface of the thorax of individual nymphs using a microcapillary tube. The nymphs were then placed in 9 cm diameter air-tight Petri dishes and maintained under ambient conditions (25-30°C and 75 ± 5% RH) for 24 hours to assess mortality and for 48 hours for metamorphic tests. The experimental design followed a completely randomized design with duplicate trials. Statistical analysis of the data revealed that the seed extract treatments exhibited significantly higher mean mortality levels of nymphs compared to the control group (P < 0.05). Among the treatments, P. guineense exhibited the highest toxicity with a mean standard error value of 16.5±2.8, followed by A. melegueta (15.0±2.7), and D. tripetala (5.5±1.7), compared to the normal control (water). The LD50 values were calculated as 22.0% w/v for P. guineense and 10.0% w/v for A. melegueta. P hytochemical analysis of the treatments revealed the presence of various secondary metabolites including flavonoids, tannins, saponins, alkaloids, terpenoids, glycosides, and anthraquinones. Among these compounds, saponins are known to disrupt cell membranes, while tannins act as polyglycosides with antifeedant properties, interfering with insect digestion. These findings suggest that the observed mortality of the cockroach nymphs may be attributed to the presence of saponins and tannins in the seed powders.