Toxicity of Vernonia amygdalina Leaf Powder against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) on Stored Cowpea (Vigna unguiculata L. Walp)

Abstract

Vigna unguiculata (L) Walps (cowpea) is an imperative bean in many unindustrialized nations used basically as one of the economical plant sources of protein. However, the grain is extensively verminous by a numeral of stowage pest amongst which Callosobruchus maculatus is a principal turf to stock irritant causing considerable excessive loss and untold hardship to farmers. Studies were therefore undertaken in the Unit of Parasitology and Entomology Laboratory at temperature of 28oC and 80% relative humidity to evaluate the effectiveness of Vernonia amygdalina foliage precipitate, used as a safe guarder against C. maculatus infiltrating stowed cowpea. The toxicity test were undertaken at five different absorptions (2.0g/mL, 1.5g/mL, 1.0g/mL, 0.5g/mL and 0.25g/mL,) of the test plant powder and (0.12g/mL) standard alpha-cypermethrin and a (0.0g/mL) untreated control per 50g of cowpea grains. Ten adults of C. maculatus remained familiarized into individual vial and the experimentation was rested out in a totally randomized design of five treatments replicated three times. The responses of C. maculatus to the insecticides and damage assessments were based on percentage mature impermanence, oviposition, F1 emergence, percentage seed impairment and percentage weight loss. At the maximum dosage (2.0g/mL/50g) of the plant powders, V. amygdalina caused mortality of 86.7% while the standard insecticides (alpha-cypermethrin) caused mortality of 86.7% and control, 13.3%. The LD50 and LD90 values of V. amygdalina were (0.43g/mL and 3.38g/mL), while LT50 and LT90 values of (150.76hrs and 487.75hrs) respectively. Analysis of variance (ANOVA) shows that these parameters were meaningfully dissimilar from the controls (P