Diatomaceous earths: Alternative insecticides to Malathion in the Soudano Guinean agro-ecological zone of Cameroon against stored maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Experiments were carried out in ambient laboratory conditions to evaluate the effect of Fossil-Shield and SilicoSec, and Malathion against Sitophilus zeamais on stored Cameroonian maize variety CMS8501. The DE products were applied at 0, 0.5, 1, 1.5 and 2 g/kg of maize grains and Malathion at 0.5 g/kg of maize. Adult mortality, F1 progeny emergence, population increase, grain damage, grain weight loss, and seed germination were evaluated. Mortality was recorded at four exposure periods, followed by F1 progeny production. Weevil population increase, grain damage, grain weight loss, and seed germination were recorded after four months of storage. Like Malathion, Fossil-Shield caused complete mortality of S. zeamais in 14 days of exposure at 1.5 g/kg, and at 2 g/kg SilicoSec achieved 96.67% mortality. Like Malathion, Fossil-Shield (99.80%) and SilicoSec (99.30%) completely inhibited the F1 progeny emergence at 2 g/kg. Fossil-Shield was the best maize grain protectant with no live insects emerging, no seed damage and no grain weight loss, SilicoSec showed similar performance at 1.5 g/kg. The DE products do not affect the seed viability. Considering these results, Fossil-Shield and SilicoSec could replace Malathion used in stored maize grains according to their same efficacy and long term protection against the weevils.