Effectiveness of N-Hexane and Ethanol Extract of Giant Calotrope ( Calotropis gigantea L.) Leaves as Insecticide Against Shallot Pest Spodoptera exigua (Hübner)

Abstract

Shallot (Allium ascalonicum) is one of the high-value plants. However, shallot productivity has been decreased due to some disturbing organisms. Spodoptera exigua is one of the pests on shallot farming and causes a yield reduction of up to 70%. Farmers use excessive synthetic pesticides to overcome the pest. The use of synthetic pesticides has several negative effects both for the environment and human beings. Therefore, natural insecticides from plants can be an alternative solution. Giant calotropes (Calotropis gigantea) is one of potential plant as natural insecticide. The research aimed to find out the most effective concentration and solvent extract of C. gigantea to give antifeedant activity and cause toxicity to S. exigua second instar larvae. The extract was obtained by gradual maceration of polar (ethanol) and non-polar (n-hexane) solvents. Secondary metabolites of the extracts were tested on thin-layer chromatography (TLC). Ethanol extract exhibits higher toxicity and antifeedant activity than n-hexane extract. The most effective concentration was 3% which caused 91,67±4,41% mortality. Ethanol extract contains a higher group number of secondary metabolites than n-hexane extract.