Sitophilus zeamais (maize weevil) is one of the most important pests of maize that cause significant deterioration of the quality and quantity of maize in storage. Ethiopia experiences an annual loss of 64% of its maize grain yield due to weevil infestations. Synthetic organophosphorus insecticides such as acetellic and malathion are still used as the primary means of controlling maize weevils in Ethiopia. However, the bulk use of these chemicals has a significant impact on human health and the environment. Recently, employing plants and their derivatives as pesticides has gained popularity as an appealing substitute in organic farming. Agarista salicifolia is one of the indigenous plants of Ethiopia, the chemical and biological activities of which are not exhaustively investigated. The leaves of the plant were extracted with ethanol and subjected to bioassay against maize weevils. The result displayed the effectiveness of the plant extract in controlling the weevil (above 80% mortality rate) at concentrations of 10 mg/mL in the laboratory at 28±3°C and RH 78±3%. The crude ethanol extract was then partitioned with solvents of different polarities: hexane, CHCl3, ethyl acetate, and methanol. The hexane and chloroform fraction showed 100% mortality at 10 mg/L concentration within 3 h of contact. Following the bioassay result, the hexane extract (2 g), which showed a similar chromatogram on its TLC profile to the chloroform extract, was packed with silica gel and applied to silica gel chromatography. Elution was made using pet ether and pet ether: EtOAc mixture with a gradual increase of polarity. Three triterpene compounds (Lupeol, alpha amyrin, and β-sitosterol) together with one straight-chain alkane were isolated from the active fraction. Alpha amyrin was tested for its insecticidal activity and exhibited activity with 100% mortality of test weevils at 10 mg/mL

Agarista salicifolia, Insecticidal activity, Maize weevil, α-amyrin and lupeol

The ethanol extract of leaves of A. salicifolia exhibited promising insecticidal activity (above 80%) against maize weevils. Our bioassay-guided study confirmed that the nonpolar extracts of A. salicifolia leaves showed 100% weevil mortality which can be used as an alternative pest management strategy for smallholder farmers. Following the bioassay-guided fractionation, four compounds (tetracosane, α-amyrin, lupeol, and β-sitosterol) were isolated from the hexane fraction. Even though α-amyrin and lupeol were isolated as a mixture, these compounds showed 100% mortality in maize weevils at 10 mg/mL concentration

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Zelalem Gizachew, Birhan Addisie, Mesfin Getachew and Mathewos Agize (2024). Insecticidal Activity of Agarista salicifolia against Sitophilus zeamais (Maize weevils). International Journal on Emerging Technologies, 15(1): 53–60.