Abstract

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

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