Assessment of the Efficacy of Actellic and Sumithion in Protecting Grains from Insect Infestation During Storage
The insecticidal efficacy of Actellic and Sumithion (2%) dusts was assessed against 0-3 day old adult Callosobruchus maculatus (Coleoptera; Bruchidae) on cowpea (Vigna unguiculata) and 0-7 day old adult Sitophilus zeamais (Coleoptera; Curculionidae) on maize (Zea mays) grains in the laboratory at 30±1°C temperature and 70±2% relative humidity. Each insect species was exposed to insecticide/grain admixtures ranging from 0.063 to 0.5 g kg-1 in comparison with untreated controls. Sumithion with LC50 values of 0.073 g kg-1 for S. zeamais and 0.104 g kg-1 against C. maculatus was more effective than Actellic (LC50 = 0.090 and 0.112 g kg-1 S. zeamais and C. maculatus, respectively) in acute toxicity tests. The efficacy of the two compounds declined as storage period increased with Sumithion showing consistent toxicity against S. zeamais. Both test compounds significantly reduced adult emergence in treated grains after infestation was established (p<=0.05). Both Sumithion and Actellic were effective at controlling C. maculatus and S. zeamais, but at admixture concentrations higher than the 0.005 g kg-1 recommended by manufacturers.
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