Honeybee propolis protects stored maize grain from damage by maize weevil (Sitophilus zeamais Motsch.) and reduces damage by larger grain borer (Prostephanus truncatus Horn) in Kenya

Abstract

The losses caused by larger grain borer (Prostephanus truncatus Horn) and maize weevil (Sitophilus zeamais Motsch.) on stored maize (Zea mays L.) grains range from 9 - 45% and 12 - 20%, respectively, depending on the storage period. These are additional losses to the field losses before harvest, threatening food security status in Kenya. With maize being a staple food consumed daily, using synthetic chemical products to manage these pests has not been easy to implement. Unaffordability of these products also forces resource-poor farmers to sell their produce early at low prices, thus compromising their food security needs. This study examined the effects of honeybee propolis extract in reducing larger grain borer (LGB) and maize weevil (MW) infestation to below economic injury level. The treatments included control, 20% propolis extract, undiluted propolis extract, Actellic super® dust, Kensil F® dust, and 20% propolis extract + Kensil F® dust. Each treatment was applied to 10g of grains, and later, 30 individuals of each insect species were introduced independently. Mortality was measured after 14 days, and all insect individuals were discarded immediately. Progeny emergence was recorded after a further 42 days. Results showed 20% propolis extract caused 48% mortality of LGB but in combination with Kensil F^® dust, the extract caused 67% mortality. In contrast, this concentration caused 100% MW mortality. Progeny emergence reduction of 16% - 26% for LGB and 100% for MW was observed in grains treated with propolis extract compared to untreated grains.

Keywords: Propolis ethanolic extract, stored maize, postharvest loss, Prostephanus truncatus, Sitophilus zeamais