Bio-efficiency of Methanolic Extracts of Leaves of Plectranthus glandulosus on Mortality and Offspring of Sitophilus zeamais F1 in Maize Protection

To find an alternative to environmentally harmful chemical pesticides, the methanolic extracts of Plectranthus glandulosus leaves were evaluated for mortality and F₁ offspring production of Sitophilus zeamais. Delvap Super® was applied as a reference insecticide at the recommended dose (0.1 g / kg), while the extracts were used at four doses (5, 10, 20 and 40 g / kg). Adult mortality was recorded daily for 14 days post-treatment. One day after exposure, Delvap Super® killed 100 % of the weevils, and the extracts caused 96.66 % mortality with the highest dose (40 g / kg). The LD₅₀ value in four days was 3.72 g / kg. From the smallest (5 g / kg) to the largest dose (40 g / kg), the extracts significantly reduced the emergence of offspring respectively 43.87 to 100 %. Considering these results, these extracts could be recommended as alternatives to synthetic insecticides against S. zeamais in storage.