Assessment of bone charcoal dusts of six species of mammal for the postharvest control of Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae) infestations of cowpea seeds: can the charcoal dust affect seed viability in laboratory and in field?

ObjectivesThe possibility that bone charcoal dusts of some species of mammal will control the major insect pest of stored cowpea seeds and the implications on seed viability (after pest control process) were investigated in the laboratory at ambient temperature (30 ± 3°C) and relative humidity (70 ± 5%) and in field.Materials and MethodsStandard entomological and agronomical techniques were used.ResultsThe results showed that at 1.0% w/w dosage, the bone charcoal dusts of Ovis aries and Bos taurus were more effective than permethrin standard insecticide in killing adult Callosobruchus maculatus Fab. infesting cowpea seeds in storage. Bos taurus had a faster action speed than permethrin at 1.0% w/w. At 1.5% w/w of dust, all the species of mammal investigated deterred oviposition considerably in C. maculatus females, whereas only the bone charcoal dusts of O. aries and Sus scrofa were comparable with permethrin in suppressing adult emergence and seed damage; S. scrofa only was comparable with permethrin in reducing larval density. Bone charcoal dusts of O. aries and S. scrofa require chemical and olfactory analyses to know if they might have caused irritation to the insects and disrupted insect circadian rhythm, affecting behaviour and mating activities, adversely. The bone charcoal dusts of the six species of mammal at a highest test dose of 1.5% w/w allowed high seed viability in both laboratory and field.ConclusionThe study recommends the use of bone charcoal dusts of O. aries and S. scrofa at economical- and quality-favourable dose 1.5% w/w for managers seeking to control C. maculatus insect attacking cowpea seeds in storage. The transitive components of the bones, abrasion of the insect epicuticle lipid layer by the charcoal dust, and combustion-related toxic factors were responsible for the insecticidal activities of the bone charcoal dusts of the mammals.