Efficacy of diatomaceous earth and botanical powders against the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) on maize

Abstract

The effectiveness of the diatomaceous earth SilicoSec, neem seed powder and Plectranthus glandulosus leaf powder, applied at four different rates with four exposure intervals (1, 3, 7 and 14 d) for the control of maize weevil, Sitophilus zeamais Motschulsky, on maize in the laboratory was determined. Treatment with SilicoSec was the most effective followed by neem seed powder and P. glandulosus powder. The highest tested content (2 g/kg) of SilicoSec caused 81.1% and 100% mortality of S. zeamais within 3 and 14 days of exposure, respectively. The application of the highest content (40 g/kg) for neem seed powder and P. glandulosus powder resulted in 86.8% and 59.5% mortality, respectively 14 days after exposure. Seven-day LC₅₀-values were 0.56 g/kg for SilicoSec, 19.7 g/kg for neem seed powder and 45.24 g/kg for P. glandulosus powder. The treatments reduced progeny emergence, percentage of grain damage, percentage of weight loss and percentage of germination loss, although P. glandulosus powder was less active for these parameters. Results suggest that SilicoSec can be considered as a potential component of an integrated pest management strategy against the maize weevil. However, in the poor tropical countries were the plant powders are widely available and food production dominated by subsistence agriculture, neem seed powder and P. glandulosus powder could be adopted also for the protection of stored maize against the infestation of S. zeamais.

Keywords: Diatomaceous earth, Botanical powders, Maize, Integrated weevil management, Sitophilus zeamais