Use of Varietal Resistance and Neem Seed Oil for the Management of Infestation of Bambara Groundnuts by Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic.)
*N.E.S. Lale1,2 and Y.T. Maina1
1Department of Crop Science, Faculty of Agriculture, University of Maiduguri, P.M.B. 1069, Maiduguri, Nigeria. Nigeria. 2Current address: Department of Animal and Environmental Biology, Faculty of Science, University of Port Harcourt, Port Harcourt, Nigeria.
Accepted in January 2004
The efficacy of an integrated pest management strategy utilizing varietal resistance and neem (Azadirachta indica) seed oil (NSO) for the control of the two bruchid species, Callosobruchus maculatus and Callosobruchus subinnotatus, jointly infesting bambara groundnuts in West Africa, was evaluated under fluctuating conditions of temperature and humidity (20-27oC and 18-54% r. h.). Three local bambara groundnut cultivars (Bakingangala, Angale and Bulmono) with varying levels of susceptibility to infestation by these two bruchid species were treated with three dosages (0.5, 1.0 and 1.5 mg/20 g seed) of neem seed oil. In each of the bambara groundnut cultivars, application of NSO especially at the rates of 1.0 and 1.5 mg/20 g seed reduced egg-laying, adult progeny development, percentage of seeds damaged by C. maculatus and C. subinnotatus, severity of damage (number of adult emergence holes per seed) and susceptibility of the bambara groundnut cultivars significantly when compared to the levels of these parameters in untreated seeds. At the dosage of 1.0 mg/20 g seed, treatment with NSO reduced susceptibility of Bakingangala, Angale and Bulmono to C. maculatus infestation by 85.2, 91.3 and 100%, respectively; comparable figures for reduction of susceptibility of Bakingangala, Angale and Bulmono to C. subinnotatus infestation were 75.0, 85.6 and 100%, respectively. At this application rate also, the proportions of damaged seeds were 24.8, 10.6 and 0.0 for Bakingangala, Angale and Bulmono, respectively; comparable values for untreated seeds were 100, 96.3 and 82.4%, respectively. No adult progeny of either species developed and no damage occurred in seeds of Angale and Bulmono that were treated with 1.5 mg of NSO.