Evaluation of cassia sieberiana (DC) and vernonia amygdalina (Del.) against callosobruchus maculatus (F.) infesting stored bambara groundnut vigna subterranea (L.) Verdc.)

Abstract

The insecticidal activity of Cassia sieberiana (DC) and Vernonia amygdalina (Del.) aqueous extract against Callosobruchus maculatus (F.) in treated bambara groundnut was evaluated under laboratory conditions (25 - 29°C and 56 - 70% r.h.). Seeds were treated separately at four concentrations (2, 4, 6 and 8 ml/100g of seeds) of both plants aqueous extracts. Pirimiphos methyl applied at 8 mg a.i./kg was included as positive control. Data collected were adult mortality, number of adult progeny (F1 and F2), percentage seed damage, percentage weight loss and germination capacity. Results showed that increasing concentration of both plant extracts and period of exposure to treated seeds significantly (P<0.05) increased adult mortality levels from 16.9±2.9 to 100%. Furthermore, both plant extracts applied at 8 ml/100 g of seeds were comparable to pirimiphos-methyl after 96 h of exposure. The plant extracts significantly (P<0.05) reduced number of adult progeny, percentage seed damage and percentage weight loss, which all progressively declined with increasing concentration from 2 to 8 ml. Both plant aqueous extracts had no effect on germination capacity of treated seeds. For all the parameters measured, the plant extracts tested showed significantly higher biological activity in treated seeds compared to the untreated control. The present results suggest that these plant aqueous extracts have the potential to control C. maculatus populations in stored bambara groundnut.