›› 2017, Vol. 60 ›› Issue (12): 1420-1429.doi: 10.16380/j.kcxb.2017.12.008

• RESEARCH PAPERS • Previous Articles     Next Articles

Effects of bioactive extracts of Ocimum canum (Lamiaceae) on Callosobruchus maculatus (Coleoptera: Chrysomelidae) in stored cowpea and soybean (In English)

Daniel KOSINI1,*, Elias Nchiwan NUKENINE2, Clément SAIDOU3, Alembert Tiabou TCHINDA4, Gabriel Agbor AGBOR4   

  1. (1. School of Health Sciences, Catholic University Institute of Saint Jérôme, Douala, Cameroon; 2. Department of Biological Sciences, Faculty of Science, University of Ngaoundere, Cameroon; 3. Department of Chemical Engineering and Environment, UIT of the University of Ngaoundere, Cameroon; 4. Medical Research Institute and Studies of Medicinal Plants (IMPM), Yaoundé, Cameroon)
  • Online:2017-12-20 Published:2017-12-20

Abstract: 【Aim】 The present study was carried out to evaluate the insecticidal, protectant and repellent potentials of hexane, acetone and methanol extracts of leaves of Ocimum canum Sims (Lamiaceae) against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae). 【Methods】 Cowpea and soybean were coated with extracts from O.canum at dosages of  1 and 5 g/kg grains and commercial neem seed oil (NSO) as a reference at the same dosages. Adult mortality of C. maculatus was assessed during a period of seven days, one day interval. Ovicidal and larvicidal toxicity was tested by treating freshly laid eggs and larvae at different immature stages of C. maculatus. Grain damage and weight loss were assessed after a storage period of four months. Repellency effects were detected in choice test using a linear olfactometer. 【Results】 Extracts had the same toxicity to C. maculatus adults and proved to be more toxic than the commercial NSO in treated cowpea. Hexane, acetone and methanol extracts caused 54.2%±3.9%, 62.9%±4.8% and 60.3%±4.5% adult mortality, respectively,within seven days of exposure to the dosage of 5 g/kg cowpea grain. Moreover, extracts evoked stronger repellency effects compared with the tested standard insecticide, irrespective of grain species. The products were the most toxic to eggs, and more toxic to 1st and 2nd instar larvae than to other developmental stages. Hexane extract was the most effective against the 2nd instar larvae (81.0%±5.3% mortality), while acetone extract (92.5%±7.5% mortality) and methanol extract (62.0%±15.7% mortality) were the most effective against the 1st instar larvae. Acetone extract had a similar toxicity with the tested standard insecticide against the 1st and 2nd instar larvae and was superior against the pupae. Cowpea grain damage and weight loss were reduced by more than three- and two-fold, respectively, after four months of storage. 【Conclusion】 The outcome of this study indicates the potential of extracts from O. canum as repellent and insecticide against C. maculatus, and because of its availability the plant is strongly recommended to be used in pest management strategies in Cameroon.

Key words: Callosobruchus maculatus, Ocimum canum, pulse, toxicity, repellency