Efficacy of solvent extracts of Calpurnia aurea (Ait.) Benth and Milletia ferruginea (Hochest) Baker leaves against maize weevils, Sitophilus zeamais (Motsch.) of stored maize in Ethiopia

Abstract

Distilled water, acetone and ethanol (polar solvent) extracts from 20 g/100 ml and 30 g/100 ml levels of extraction of Calpurnia aurea and Milletia ferruginea were tested as protectant against maize weevils in maize grains under laboratory condition. They were applied at a rate of 10 and 15% (w/v) in admixture bioassays from both of the aforementioned extraction levels. Parental weevil’s mortality, F1 progeny emergence, percent protection, grain damage and weight loss were the parameters measured. All polar solvent extracts of the tested plants applied at a rate of 10 and 15 ml from the two extraction levels induced significant (p≤0.05) toxicity effect against weevils than solvent treated grains at all dates after treatment. Besides, significantly (p≤0.05) higher mortality of parental weevils were recorded in all polar solvent extracts (>75%) of the tested botanicals applied at 15 ml dosages from 30 g/100 ml extraction levels than those applied at a rate of 10 ml following 96 h treatment application. Furthermore, all the polar solvent extracts applied at rates of 10 and 15% also induced good degree of protection of maize grains (≥78%) against F1 progeny emergence, percent grain damage (≤1.33) and weight loss (≤0.28) by maize weevils than negative control in about 2 months storage period (56 days). Consequently, the solvent extracts of C. aurea and M. ferruginea were potent and therefore, they can be used in management of maize weevils in stored maize under subsistence farmer’s storage conditions. Key words: Calpurnia aurea, Milletia ferruginea, Sitophilus zeamais, botanicals, polar solvent extracts, stored maize.