<jats:title>Abstract</jats:title><jats:p><jats:bold>BACKGROUND:</jats:bold> Tropical plants are recognised sources of bioactive compounds that can be used for pest control. The objective of this study was to evaluate the biological activity of compounds present in <jats:bold><jats:italic>Acmella oleracea</jats:italic></jats:bold> (Asteracea) against <jats:bold><jats:italic>Tuta absoluta</jats:italic></jats:bold> (Meyrick) (Lepidoptera: Gelechiidae), which is the main pest of tomato crops in Latin America. The selectivity of these compounds to the predator <jats:bold><jats:italic>Solenopsis saevissima</jats:italic></jats:bold> (Smith) (Hymenoptera: Formicidae) and to the pollinator <jats:bold><jats:italic>Tetragonisca angustula</jats:italic></jats:bold> (Latr.) (Hymenoptera: Apidae: Meliponinae) was also of interest.<jats:p><jats:bold>RESULTS:</jats:bold> A bioassay screening with hexane and ethanol extracts from 23 plants was performed. The hexane extract of <jats:bold><jats:italic>A. oleraceae</jats:italic></jats:bold> was the most active of the extracts and was selected for further study. The following three alkamides were isolated from a hexane extract of the aerial parts of <jats:bold><jats:italic>A. oleracea</jats:italic></jats:bold>: spilanthol, (<jats:italic>E</jats:italic>)‐<jats:italic>N</jats:italic>‐isobutylundeca‐2‐en‐8,10‐diynamide and (<jats:italic>R</jats:italic>, <jats:italic>E</jats:italic>)‐<jats:italic>N</jats:italic>‐(2‐methylbutyl)undeca‐2‐en‐8,10‐diynamide. All of the isolated compounds showed insecticidal activity, with spilanthol being the most active (LD<jats:sub>50</jats:sub> = 0.13 µg mg<jats:sup>−1</jats:sup>) against <jats:bold><jats:italic>T. absoluta</jats:italic></jats:bold>. The alkamides were selective to both beneficial species studied.<jats:p><jats:bold>CONCLUSION:</jats:bold> The crude hexane extract of <jats:bold><jats:italic>A. oleraceae</jats:italic></jats:bold> showed high insecticidal activity and can be used to control <jats:bold><jats:italic>T. absoluta</jats:italic></jats:bold> in organic or conventional crops. Quantification of LD<jats:sub>50</jats:sub> values of isolated compounds against <jats:bold><jats:italic>T. absoluta</jats:italic></jats:bold> showed that alkamides could serve as potent insecticides for <jats:bold><jats:italic>T. absoluta</jats:italic></jats:bold> control programmes. Spilanthol was the main alkamide active isolated. This alkamide is the most promising as it has the highest insecticidal activity and is selective to non‐target organisms. Copyright © 2011 Society of Chemical Industry