Dosage rates of 1.25, 2.5, 5 and 10% (w/w) of red and white locally available inert dusts were evaluated as protectants against maize weevils, Sitophilus zeamais in maize grain under laboratory conditions. Parental adult mortality, F1 progeny emergence, percent protection, percent grain damage and weight loss were measured as efficacy determining parameters. Mortality of the weevils was observed only after 4 days post exposure and mean percentage mortality of the parental weevils caused by both inert dusts were significantly (P < 0.05) higher compared to untreated controls. Significant death of adult weevils was found to be induced gradually as from day 14 post exposure by both dusts when applied at the lower rate of 1.25 and 2.5%. Mortality with higher dosage rates of 5 and 10 % was observed as from day 7 after exposure. At day 21 post exposure, all dosage rates of both inert dusts and the positive control induced 100% weevil mortality. Both inert dusts applied at higher dosages 5 and 10% caused significantly (P < 0.05) higher (52.64%) protection of maize grain against F1 progeny emergence, percent grain damage (6.33%) and weight loss (2.33). Thus, the tested inert dusts were potent at a rate of 5 and 10%, and have the potential to be used in managing maize weevils under farmer’s storage conditions following field trials.
Key words: Red inert dust, white inert dust, Sitophilus zeamais, stored maize.
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