Fumigant Activity of Four Plant Powders against Cowpea Weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae) in Stored Adzuki Bean

Background: Cowpea weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae) is one of most common species pest that attack various types of beans in the storage. Plant-based insecticides are considered as good candidates as alternatives to methyl bromide and phosphine for controlling pest in storage. Plenty of reports about plant powder as grain protectant, conversely a little information on plant powder as fumigant had been reported. This study was designed to observe the effects of plant powders of clove, holy basil, lemongrass and turmeric as fumigant on the biological parameters of C. maculatus under laboratory conditions. Methods: Experiments were conducted on plant powders against biological parameters of cowpea weevil. No choice test method was followed to assess the bioefficacy of the four natural fumigants on adult longevity, fecundity, F-1 progeny, bean damage and weight loss of bean under completely randomized design (CRD). Result: Fumigant toxicity of four plant powders (clove, holy basil, lemongrass and turmeric) varied amongst doses. Clove powder showed significantly lower adult longevity, fecundity of female, number of F-1 progeny, bean damage and weight loss of bean at 1 g and 3 g dose per container. Major volatile organic compounds (VOCs) in clove powder were eugenol (48.64%) and caryophyllene (43.09%) identified by solid phase microextraction followed with gas chromatography and mass spectrometry (SPME-GC/MS). These two major constituents might explain the fumigant toxic activities of clove powder towards C. maculatus biological parameters.