Synergetic effects of two botanical entomocides as pest-protectants in maize grains

Sitophilus zeamais Motschulsky infestation causes severe post-harvest losses of cereal grains in Nigeria leading to major nutritional and economic losses. A laboratory study was conducted to determine the efficacy of Myrcianthes fragrans and Aframomum melegueta seed powders and methanol extract as well as their synergetic effects on S. zeamais. The ability of the plant products to protect maize grain against S. zeamais infestation was assessed in terms of mortality 24 to 96 h posttreatment, oviposition, and adult emergence, weight loss and grains damage. M. fragrans and A. melegueta products significantly cause adult mortality of S. zeamais. M. fragrans products were the most toxic as it evoked 100% adult mortality within 24 h of application while A. melegueta products evoked 100% mortality of S. zeamais at 48 and 72 h post treatment, respectively. The synergetic effects of the plant products caused 100% adult mortality at 48 and 72 h post-treatment, respectively. Oviposition, adult emergence, weight loss and damage of the maize grains treated with the plant products were completely inhibited compared with untreated grains. The results obtained revealed that 2 g and 2% sole application of M. fragrans and mixed application of M. fragrans and A. melegueta products were effective in controlling Sitophilus zeamais post-harvest infestation and grain damage and could serve as an alternative to synthetic insecticide in ensuring steady supply of maize grains, thus ensuring food security as the plants are of medicinal and nutritional quality.