Evaluation of some plant products for the management of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae) in stored maize (Zea mays) and their effect on nutritional composition of the kernels

Abstract

The bioactivity of powder from the leaves of Aristolochia ringens, Dalbergia saxatilis, Dioclea reflexa, Ocimum gratissimum, Chrysophyllum albidum, Moringa oleifera, Citrus limon and Newbouldia laevis was tested against the larger grain borer (LGB) in maize kernels and the effect of the powder on the nutritional composition of the kernels was determined. A total of 72 glass bottles containing 100 g maize kernels was divided into four groups. In the first group of 32 glass bottles, 5 g powder of the experimental plants was admixed uniformly with the kernels (5% w/w). Ten 1–5-day-old LGB adults were introduced into each of the glass bottles. A second group of 32 glass bottles contains 100 g maize kernels admixed with the plant powder as described above, but LGB were not added. In the third group of four glass bottles, 100 g maize kernels received insects only, while in the fourth group of four glass bottles 100 g maize kernels were neither mixed with plant products nor infested with LGB. The treatments were arranged on worktables using completely randomised design and left for three months. The plant products-treated samples (insect free) were passed through a 30 mesh sieve to sieve out the powder and the clean kernels were analysed for proximate composition. The untreated maize kernel had a significantly (p < 0.05) higher % of grain weight loss (17.33), grain damage % (70.96), number (122.0) of adult LGB, weight (14.46 g) of grain dust and lower % of grain germination. The adsorption and absorption of some of the plant powder by the kernels had significant effect on the kernel composition of protein, fibre and carbohydrate, but not on moisture, dry matter and fat and ash content. Control of LGB with the powder of the test plants could be used as green insecticide for the management of LGB.

Keywords:

• bioactivity
• larger grain borer
• maize kernels
• nutritional composition
• infestation