Laboratory evaluation of five botanicals as protectants against cowpea bruchid Callosobruchus maculatus F. (Coleoptera: Bruchidae) on stored cowpea

Abstract

Cowpea (Vigna unguiculata L. Walp) is an important legume grown primarily in the tropics. Cowpea bruchid Callosobruchus maculatus is a major pest of stored cowpea in Nigeria. A laboratory study was conducted to evaluate the effectiveness of some indigenous botanical powders and one essential oil extract as grain protectants against C. maculatus at Agronomy Laboratory, Michael Okpara University of Agriculture Umudike in 2013. The treatments applied were 1.5 g powder each of tumeric rhizomes, garlic bulb, sand paper leaves, bitter kola seeds, ginger rhizomes, 0.5 ml of ginger rhizome essential oil and a control. The experiment was laid out in Completely Randomized Design (CRD) with four replicates. Adult mortality, progeny emergence, percentage grain damage, percentage weight loss and germination percentage were assessed. The result obtained showed that all the botanicals gave protection to the stored cowpea seeds compared with the control. Botanical extracts did not affect percentage stored cowpea weight loss (P > 0.05). All the botanicals significantly (P < 0.05) reduced the grain damage of cowpea seeds by C. maculatus and F1 progeny emergence. The total number of C. maculatus adults that emerged from untreated control progressively increased with time of exposure compared to the other treatments. Significantly higher germination percentage was recorded in the various treatments with botanicals compared with the control which recorded 35%.

Keywords: Botanicals, Callosobruchus maculatus, control, damage, mortality.