Efficacy of Single and Combined Leaf Powder of Nicotiana Tabacum L. [Solanales: Solanaceae] with Reduced Rates of Pirimiphos-Methyl in Management of Sitophilus Zeamais Motschulsky [Coleoptera: Curculionidae]

The toxicity effects of the combination of Nicotiana tabacum leaf powder and pirimiphos-methyl dust as atreatment is compared with sole treatment of the powder and dust in this study. All laboratory experiments wereconducted under prevailing conditions of 28±30C and 70±5% relative humidity. Contact toxicity of Nicotianatabacum powder was tested on Sitophilus zeamais at 0.4g and 0.01g of pirimiphos-methyl powder per 20g ofmaize seeds singly. The toxicity of combined powder of N. tabacum at 0.2g with 0.0013g, 0.0025g and 0.005g ofpirimiphos-methyl dust per 20g of maize seeds was also tested. These treatments significantly (p>0.05) reducedthe weight loss and adult emergence of S. zeamais. The powder and dust also caused high mortality to S. zeamaiswhen applied.The efficacy of the Nicotiana tabacum was better when applied singly at 0.4g than when combined with dust ofpirimiphos-methyl at reduced rates. Irrespective of the treatment used in the study, the response of Sitophiluszeamais was found to be dependent on the concentration. Adult mortality increases with concentration, whileadult emergence reduces. The results of this study revealed the effects of combined botanicals with reduced ratesof conventional insecticides as an alternative in the management of stored product insect pests.