Potent insecticidal activity of Eleocharis dulcis peel extract and its main components against aphids

Aphids are significant pests of the cash crops and food farm crops. Botanical insecticides are safe for aphid control, especially in organic agriculture. In this study, Eleocharis dulcis peel extract (EDPE), a new botanical insecticide, was investigated for its active compositions against several agricultural aphids. The results showed that the EDPE had high insecticidal activity against Sitobion avenae , Aphis gossypii , Megoura crassicauda , and Acyrthosiphon pisum , with the half lethal concentration (LC 50 ) values of 95.92, 81.04, 140.31, and 255.73 mg/L after 48 h treatment. In the pot culture assay, the aphicidal effects of 25% EDPE soluble liquid (SL) at a concentration of 0.016% were 68.98%, 79.33%, and 88.82% after the 1st, 3rd, and 7th days of treatment, respectively. Nine compounds were identified by bioactivity-directed fractionation, which was dimethoxy-6, 6-dimethylpyranoisoflavone ( 1 ), 3-methoxy-4-hydroxylonchocarpin ( 2 ), 4-hydroxylonchocarpin ( 3 ), 4-methoxylonchocarpin ( 4 ), barbigerone ( 5 ), lonchocarpusone ( 6 ), 6a, 12a-dehydrodeguelin ( 7 ), 13-homo-13-oxa-6a,12a-dehydrodeguelin ( 8 ) and deguelin ( 9 ). Among them, 4-hydroxylonchocarpin ( 3 ) showed the highest aphidicidal activity against M. crassicauda , S. avenae , and A. pisum , with the LC 50 values of 97.24, 140.63, and 112.31 mg/L, respectively. Therefore, EDPE and its major component 4-hydroxylonchocarpin are probably used as new botanical insecticides to control aphids.