Comparative efficacy of Jatropha curcas L. leaf powder for the control of Callosobruchus subinnotatus (Pic) on stored bambara nut Vigna subterranea (L.) Verdcourt

Abstract

The research was conducted in the year 2016 at the Entomology laboratory of the Department of Crop Protection, Bayero University Kano to assess the biocidal and damage reduction effect of leaf powder from physic nut, Jatropha curcas L. caused by Callosobruchus subinnotatus (Pic) on stored bambara nut, Vigna subterranea (L.) Verdcourt. Also, the study aimed at comparing the effectiveness of the plant product with conventional chemical insecticide (pirimiphos-methyl). Factorial experiment of 4×2 levels (leaf powder at the rates of 0, 0.5. 1.0 and 1.5 g, with and without addition of the synthetic chemical at 0.01 g/20 g bambara nut seed) were laid out in a Completely Randomized Design and repeated three times. Results showed that, admixture of 0.5g leaf powder proved effective in causing high biocidal effect and reduced seed damage. However, this was statistically same with seeds treated with 1.0g leaf powder. Comparatively, all treatments were statistically different from the untreated control seeds but similar with the check treatment. Highly significant (p<0.001) persistent effect was observed in seeds treated with 1.5g leaf powder mixed with 0.5g seed powder at 60 days after treatment (DAT) without any negative effect on seed viability. This was also statistically similar in all other treatments apart from the untreated control. In conclusion, appreciable level of protection on bambara nut seeds was achieved using leaf and seed powder of J. curcas applied at different mixture rates and singly. Therefore, it is recommended that for effective management of C. subinnotatus infesting bambara nut, farmers could use 1.5 g leaf powder or 1.0 g seed powder per 20 g bambara nut seeds singly each. Alternatively, 0.5:1.0, 1.0:1.0 or 1.5:0.5 leaf/seed combinations could be used for safe bambara nut storage.

Keywords: Biocidal, Callosobruchus subinnotatus, bambara nut, Jatropha, damage, insecticide