Efficacy of Integrating Varietal Resistance and Neem (Azadirachta indica A. Juss) Seed Oil for t,e Management of Callosobruchus maculatus Infesting Bambara Groundnuts in Storage

Abstract

The efficacies of three rates (0.5, 1.0 and 1.5 mg/20 g seed) of application of neem (Azadirachta indica) seed oil (NSO) in controlling Callosobruchus maculatus infesting stored bambara groundnut were assessed on four local cultivars (Ole, Bakingangala, Bulmono and Jor) with different susceptibilities to bruchid attack. Untreated batches of the cultivars were included to serve as control. Treated and untreated batches were infested with adults of C. maculatus under prevailing storage conditions. Combining application of NSO especially at the rate of 1.5 mg/20 g seed with varietal resistance significantly reduced oviposition and progeny development in C. maculatus. No adult progeny developed in seeds of Bakingangala that were protected with 1.5 mg of oil. Treatment of seeds with NSO at this rate reduced seed damage from 97, 72.3, 58.1 and 87.90.4in unprotected Ole, Bakingangala, Bulmono and Jor to 3.0, 3.4, 0.0 and 18.3%, respectively. The interaction of the strategies also significantly reduced the severity of damage (number of adult emergence holes per seed) and overall susceptibility of the bambara groundnut cultivars. Susceptibility indices (SI) values for unprotected bambara groundnuts were 11.92, 10.52, 9.09 and 11.43 for Ole, Bakingangala, Bulmono and Jor, respectively. Comparable SI values for bambara groundnuts that were treated with NSO at the rate of 1.5 mg/20 g seed were 0.0, 1.12, 0.0 and 2.82 for-Ole, Bakinganpla, Bulmono and Jor respectively.