Toxicity of pirimiphos-methyl and three essential oils, viz. cardamom [Elettaria cardamomum (L.) Maton.], cinnamon (Cinnamomum aromaticum Nees) and clove [Syzygium aromaticum (L.) Merr. & Perry]; either singly or in mixture in different ratios were investigated on the cowpea weevil, Callosobruchus maculatus (F.) adults, through residual film bioassay. The LD 50 of pirimiphos-methyl was 0.011 µg cm -2 and that of cardamom, cinnamon and clove oils were 20.68, 12.38 and 16.89 µg cm -2 respectively

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... after 24 h post-treatment. Pirimiphos-methyl and tested essential oils were used as mixture of 1:1, 1:2, 1:5, 1:10 and 1:20 and the LD 50 values were calculated. All essential oils when combined with pirimiphos-methyl proved to be antagonistic effect against C. maculatus adults except cardamom oil which offered synergistic effect at the 1:20 ratio with pirimiphos-methyl.