ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 93 Number 3
Susceptibility of the life stages of Callosobruchus maculatus (Fabr.) in stored cowpea grains to fumigation with essential oil vapour of Ocimum basilicum L. leaves. (178)
This study was carried out to investigate the susceptibility of the life stages of Callosobruchus maculatus (F.) in stored cowpea to the essential oil vapour of sweet basil, Ocimum basilicum, L.leaves when applied as a fumigant. The extracted and analysed essential oil of O. basilicum leaves in this study was made up mainly of monoterpenoids and sesquiterpenoids with ?-terpinene (12.2%), and ?-caryophyllene (10.4%) predominating. In separate bioassays, cowpea seeds harbouring the different life stages of C. maculatus were exposed to the oil vapour within a hermetic structure. The essential oil vapour had insecticidal effects on the adults of C. maculatus. Mortality was observed to significantly (P<0.05) increase from 14.8% to 100% as dosage increased from 10µl/80ml air to 60µl/80ml air. Significantly high percentage mortality (98.48%) of C. maculatus eggs was observed after three days of seed fumigation with the essential oil vapour. The percentage mortality caused by the oil vapour to the larval and pupal stages within fumigated cowpea seeds was not significantly different from the control at P=0.05 after three days of fumigation. It was thus concluded that the egg and adult stages of C. maculatus were more susceptible to the essential oil vapour of O. basilicum leaves than the larvae and pupae stages within stored cowpea.
Keywords: Callosobruchus maculatus, ocimum basilicum, essential oil, fumigation, cowpea Crops