Effects of paracress (Acmella oleracea) extracts on the aphids Myzus persicae and Lipaphis erysimi and two natural enemies

Abstract

This study was conducted to evaluate the toxicity of paracress (Acmella oleracea) extracts to the aphids Myzus persicae (Sulz.) and Lipaphis erysimi (Kalt.) (Hemiptera: Aphididae), and the extracts selectivity to the aphid parasitoid Diaeretiella rapae McIntosh (Hymenoptera: Braconidae) and to the predator Orius insidiosus (Say) (Hemiptera: Anthocoridae). We evaluated water and ethanol extracts from A. oleracea. The ethanol extract caused 90% mortality of both aphid species within 70 h and reduced their fecundity, whereas the water extract was inactive. In addition, this extract caused no mortality of the natural enemies. In an attempt to identify bioactive compounds in the ethanol extract, three alkamides, spilanthol, undeca-2E-en-8,10-diynoic acid isobutylamide (compound 2) and (2E)-N-(2-methylbutyl)-2-undecene-8,10-diynamide (compound 3), were isolated and tested on L. erysimi. From the isolated alkamides, spilanthol and compound 2 showed high insecticidal activity against L. erysimi, indicating that they contributed to the observed extract activity. The results of this study demonstrate the potential of the ethanol extract of A. oleracea as a botanical insecticide in the management of aphids in brassicas.