Research Article

Use of volatile oils of garlic to control the cowpea weevil Callosobruchus maculatus (Bruchidae: Coleoptera)

Published in: South African Journal of Plant and Soil
Volume 34, issue 3, 2017 , pages: 185–190
DOI: 10.1080/02571862.2016.1225232
Author(s): Mahgoub I AbdallaDepartment of Crop Science, Faculty of Natural Resources and Environmental Studies, Sudan, Azhari O AbdelbagiDepartment of Crop Protection, Faculty of Agriculture, Sudan, Ahmed MA HammadDepartment of Crop Protection, Faculty of Agriculture, Sudan, Mark D LaingDiscipline of Plant Pathology, School of Agricultural, Earth and Environmental Sciences, South Africa

Abstract

Cowpea weevil causes losses of 50–90% in cowpea after harvest. Control has relied on toxic agrochemical fumigants that are no longer available or are dangerous and relatively expensive, making its control difficult for most farmers. This study was initiated to investigate alternative control methods to synthetic pesticides, namely the suitable fumigation period and oil concentration of volatile oils of garlic, Allium sativum, were evaluated as a fumigant against adults of the cowpea weevil, Callosobruchus maculatus (Bruchidae: Coleoptera). Fumigation was carried out in small plastic cups (200 mL) and jute sacks (100 g) after several exposure periods (6–24 h). Insect recoveries were observed for 4 d. The volatile oils were tested at concentrations ranging between 0.1% and 20% (v/v). The oils were effective and caused significant mortalities to the test insects in cups at all concentrations tested. Garlic oil vapour penetrated through jute sacks and caused significant mortality to test insects. Recovery cases were negatively correlated to the dose. The 24 h LD50 and LD90 were 0.036% (equivalent to 175.78 μL volatile oils m−3) and 3.61% (equivalent to 17.63 mL volatile oils m−3), respectively, in the cups and jute sacks. The concentration 10% gave 100% mortality within 24 h of exposure.

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