Preservation of Cowpea (<em>Vigna unguiculata</em>) Seeds: Incidence of Ethanolic Extract from <em>Balanites aegyptiaca</em>, <em>Melia azedarach</em> and <em>Ocimum gratissimum</em> Leaves on <em>Callosobruchus maculates</em> (Coleptera: Bruchidae)

Abstract

This study aims to evaluate the effect of ethanolic extracts of Balanites aegyptiaca, Melia azedarach and Ocimum gratissimum leaves as bioinsecticide in the preservation of cowpea seeds (Vigna unguiculata) against the pest Callosobruchus maculatus. The extracts were obtained by maceration of leaves powdersin ethanol (95%). These extracts were then used to achieve anti-insecticides tests in jars at doses of 10, 15, 25 and 50% compared to a reference compound (Stargrain). The weevils rearing and some biological tests were conducted in laboratory conditions at a temperature of 29.1°C and a relative humidity of 74%. The results showed that these extracts have anti-oviposition activity and ovicidal dose-dependent. Doses 25 and 50% of Melia azedarach and Ocimum gratissimum have completely inhibited the spawning activity of C. maculatus 24 h after treatment. There was significant difference (p<0.05) between oviposition due to the positive control (Stargrain) and that due to dose 50% of the three extracts. Compared to the negative control (ethanol 95%), all these plant extracts have significantly reduced (p<0.05) oviposition of C. maculates female (38 eggs per 100 seeds after 4 days). The dose 10% of B. aegyptiaca and 50% of O. gratissimum showed no weevil emergency. It have been also noticed a reduction in seeds depreciation and rate attack in all the treated settings compared to the control. So the rate attack and the mass loss were proportional to the doses of B. aegyptiaca leaves extract but conversely proportional to doses of Melia azedarach and O. gratissimum leaves extracts. No depreciation of seeds was recorded at doses 10 and 15% of B. aegyptiaca and 50% of O. gratissimum. The different treatments did not affect the germination of seeds; the highest germination rate (93.67%) was recorded with seeds treated with the dose 50% of O. gratissimum against only 65% with those treated with the positive control. These ethanolic extracts have shown insecticidal effect against C. maculatus and can alternatively use for the cowpea seeds preservation.

Germination and seedling emergence responses of common bean and cowpea to plant extract seed treatments

“…In agreement with the findings of the present study, WIPO (2007) also reported that the crude extracts of flowers, flower stalks, leaves and aerial parts of Agapanthus africanus increased germination of radish ( Raphanus sativus L.) seeds when compared with the water control. Furthermore, in a study by Miafo et al (2014) the germination of cowpea seeds was unaffected after treatment with ethanolic leaf extracts of Balanites aegyptiaca (L.) Del., Melia azedarach L. and Ocimum gratissimum L.…”