Efficacy of bone charcoal dust of six mammalian species as eco-friendly alternatives to conventional synthetic insecticides in the control of Sitophilus Zeamais Motschulsky (Coleoptera : Curculionidae) infesting stored resistant and susceptible maize cultivars

The efficacy of bone charcoal dusts of six species of mammal as eco-friendly alternatives to conventional synthetic insecticides in the management of Sitophilus zeamais Motschulsky infestation in stored resistant and susceptible maize cultivars was investigated in the laboratory at ambient temperature (31.8 0C) and relative humidity (70.5 %). Dry femurs and ribs of the African humped cow (Bos indicus Linnaeus), rabbit (Lepus spp L.), goat (Capra hircus L.), sheep (Ovis aries L.), dog (Canis domesticus L.) and pig (Sus scrofa L.) were burnt with fire wood (Magnifera indica L.). The resulting bone charcoal was ground using clean mortar and pestle, and sieved to produce the fine inert dust for the assay. Bone charcoal dusts of the animals and permethrin powder were comparatively tested at the rates of 0.25, 0.50 and 1.00 % w/w against S. zeamais infesting stored resistant and susceptible maize. The charcoal dusts of cow and sheep were the best at controlling S. zeamais infestation. After matching with the efficacy of permethrin, the study found that bone charcoal dusts of the mammals could be exploited in the control of weevil infestation in both stored resistant and susceptible maize cultivars. Complete suppression of S. zeamais progeny emergence and 100 % grain protection from pest-feeding were achieved with ≥ 0.25 % (w/w) of each of the animal bone charcoal dust in resistant maize stored for 54 days. However, in susceptible cultivar, higher dust concentration of ≥ 0.50 % (w/w) was needed to achieve the same results. High mortality and protection achieved by the bone charcoal dusts were attributable to weevil cuticular abrasion, active components of the bones and combustion-related factors. Class of maize cultivar stored and protected with the animal bone charcoal dusts had no obvious impact on the weevil mortality at short storage duration of < 5 days. However, at prolonged storage duration of 54 days, cultivar-effect became conspicuous in terms of adult emergence and grain damage