Evaluation of the Fumigant Action of Garlic (Allium sativum) Aqueous Extract Against the Cowpea Seed Weevil Callosobruchus maculatus, (F.)

Abstract

The efficacy of the fumigant action of garlic aqueous ethyl acetate extract (95:5 v/v) from the Chinese garlic was tested against the adult stage of the cowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), under laboratory conditions at the Department of Crop Protection, Faculty of Agriculture, University of Khartoum, Shambat, Sudan. Garlic extracts were prepared by 24 hrs soaking of garlic powder in water: ethyl acetate solution (95:5% v/v). The tested concentrations were 0.1%, 1%, 5% and 10%. The bioassay was done in plastic cups placed in glass chambers with sliding doors. Result indicated that water: ethyl acetate extract was effective against the test insect. The median lethal doses (LD₅₀) for the extracts after 6, 12, 24, 48 and 72 hours were 0.351%, 1.14%, 0.26%, 0.088% and 0.059% while the corresponding LD90 values were 14.92%, 7.41%, 1.66%, 2.99% and 1.20%. The respective median lethal times (LT₅₀) values at the concentrations 10%, 5%, 1% and 0.1% were 3.56 hrs, 4.35 hrs, 9.87 hrs and 50.63 hrs with a corresponding LT₉₀ of 16.32 hrs, 19.09 hrs, 63.86 hrs and 112.39 hrs. Mortality was found to increase with increase in exposure period and concentration. The responses of test insects were homogenous as indicated by the steep slope of probit lines. Based on the current results 90% mortality can be achieved at concentration 5% within 24 hrs exposure period. No significant recoveries were observed after 4 days following exposure and few non-significant cases of malformation were noticed. Further lines of research were suggested.