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Toxicity of some biopesticides to <i>Sitophilus zeamais</i> motschulsky on maize in storage


O.I Mbah
M.N Okorie

Abstract

Potentials of plant derived pesticides (Monodora myristica Gaertn) Dunal and Aframomum melegueta (Rosch) each at 3 concentrations of 5, 10 and 15g were evaluated in the laboratory against the stored pest of maize Sitophilus zeamais. The Aframomum treatments, which achieved adult mortality of 64%, 63% and 45% in week 1 at the three dosage levels of 15, 10 and 5g per 150g maize in that order was not as potent as Monodora powder in the control of S. zeamais. It was however, obvious that pirimiphos methyl and the two doses of Monodora proved very efficacious in the control of the weevil with 100%, 83% and 72% mortality respectively. Pirimiphos methyl offered complete inhibition of post-embryonic development, followed by Monodora treatments, which also remarkably halted progeny emergence. Aframomum treatments were less effective though significantly better than the control. Grains treated with pirimiphos methyl and Monodora were better protected against damage than Aframomum treatments. No weight loss was recorded in Pirimiphos methyl treated grains, and only marginal losses were observed in Monodora treatments as a result of insect activities compared to the increased weight loss in Aframomum treatments, which were nevertheless significantly heavier than the control grains. The test botanicals did not exert adverse effects on seed quality, taste and viability after storage.

Keywords: Toxicity, biopesticides, S. zeamais, stored maize


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print ISSN: 0300-368X