Toxicity of essential oils used for the protection of stored cowpea against callosobruchus maculatus f. Coleoptera:bruchidae)

Plant essential oils of Ocimum basilicum, Acorus calamus, Thuja occidentails, Thymus vulgaris, Tagetes bipinata and Origanum majorana, were evaluated as grain protectant against the cowpea weevil Callosobruchus maculatus (F.) in the laboratory at 200, 400 and 600 ppm concentrations. Parameters assessed were adult mortality, rate of adult emergence, grain damage and weevil perforation index (WPI). Data pertaining to the above experiments clearly indicated that there was an increase in adult mortality with days of exposure in all concentrations. Ocimum basilicum, Acorus calamus, Thauja occidentalis and Origanum majorana were promisingly controlled the bruchid infestation on the experimental grains. From this we inferred that Ocimum basilicum, Acorus calamus, Thauja occidentalis and Origanum majorana could be a potent biopesticide, for protecting cowpea grains from C. maculates infection and daomage. The details of the bioassay procedures used and the results obtained in the present experimentation were discussed in the light of recent literature. These findings are first hand information about efficacy of selected oils against C. maculatus.