Herbicidal and fungicidal activities and identification of potential phytotoxins from Bidens pilosa L. var. radiata Scherff

This study was carried out to examine the possibility of utilizing Bidens pilosa , a weed widely distributed in the subtropics and the tropics, for weed and plant fungus control. The extract of B. pilosa shows strong phytotoxic action against the growth of Raphanus sativus and Echinochloa crus‐galli and antifungal activity against phytopathogens in bioassays. The extract of the roots exhibited plant growth inhibitory activity more than those of the leaves and stems. Fifteen phenolic compounds, including pyrocatechin, salicylic acid, p ‐vinylguaiacol, dimethoxyphenol, eugenol, 4‐ethyl‐1,2‐benzenediol, iso‐ vanillin, 2‐hydroxy‐6‐methylbenzaldehyde, vanillin, vanillic acid, p ‐hydroxybenzoic acid, protocatechuic acid, p ‐coumaric acid, ferulic acid, and caffeic acid were identified by gas chromatography–mass spectrometry. Caffeic acid was in the highest amount among the detected substances. Dimethoxyphenol and vanillic acid were found only in the roots of B. pilosa . Ferulic acid and p ‐hydroxybenzoic acid were higher in the roots than in the leaves and stems. These identified constituents might be responsible for the phytotoxic and fungitoxic activities of B. pilosa.