Efficacy of four protectants applied to stored bambarra groundnut against infestation by Callosobruchus maculatus (Fab.)

Abstract

Bambara groundnuts are good nutrient sources of high protein and carbohydrate contents. The seeds suffer damage through infestation by Callosobruchus maculatus (Fab.) during storage. The efficacy of four protectants, namely actellic, steam, neem seed oil and neem kernel oil were tested on two varieties of Bambara groundnuts namely, Jabajaba and Piele Balgu. Efficacy of the different treatments was demonstrated on Bambara groundnut through the number of adult C. maculatus that emerged. Actellic, steam and neem seed oil significantly (P<0.05) reduced emergence of C. maculatus on the seeds of the varieties used. Consequently these treatments also significantly (P<0.005) reduced the number of seeds that were damaged through C. maculatus infestation. Damage of seeds of the Piele Balgu variety ranged from 1.1 (actellic treated) to 30.4 (neem kernel oil treated). In the Jabajaba variety, seed damage ranged from 1.1 (actellic treated) to 28.6 (untreated). Each of the four treatments, however, significantly (P<0.05) reduced C. maculatus infestation in the order of Actellic >Steam > Neem seed oil > Neem kernel oil. Persistence of treatment effects were tested for 90 days after treatment (due to time constraint). It was established that the seed testa of Jabajaba Bambara groundnut renders it less susceptible to C. maculatus infestation. Actellic did not lose its efficacy 90 days after treatment. Steam and neem seed oil significantly (P<0.05) reduced infestation of legumes by Callosobruchus maculatus. Germination of treated seeds showed that steam treatment had a lethal effect on the \ seeds used. Neem seed oil promoted germination whilst Actellic significantly (P<0.05) reduced the activity. Neem seed oil promoted more vegetative growth in the Piele Balgu variety than in the jabajaba variety. Protein content of treated Bambara groundnut seeds did not change significantly (P>0.05) from the untreated. Seeds of the jabajaba variety have more protein than the Piele Balgu seeds which were instead more susceptible to C. maculatus infestation. Neem seed oil offers a good protection to seeds of Bambara groundnut, does not affect the protein content and germination potential of seeds and can therefore be used as a substitute for actellic.