The potential of Myosoton aquaticum extracts and compounds to control barnyardgrass (Echinochloa crus‐galli).

Although cover crops are widely used for weed suppression in the agroecosystem, little research is available regarding the possibility that the decomposed weed solution may control weeds. In this study, we tested the allelopathic effect of decomposed weed solution on barnyardgrass (Echinochloa crus‐galli). In two separate tests, we found that the solution of decomposed Myosoton aquaticum completely suppressed the germination of barnyardgrass seeds at a concentration of 20 g l‐1. We then isolated and identified the predominant inhibitory substance in the decomposed M. aquaticum solution. The solution was subjected to organic solvent extraction and then separated on a silica gel column before the final identification of its components by high‐performance liquid chromatography‐tandem mass spectrometry (HPLC‐MS/MS). Dihydrocoumarin was isolated from the M2 and M3 fractions using a bioassay‐guided method and was found to be the most active of eleven candidate allelochemical compounds. Dihydrocoumarin is typically used as a food additive. In this study, barnyardgrass germination was completely inhibited when treated with dihydrocoumarin at 1 g l‐1, and its root and shoot growth were significantly inhibited at an application rate of 0.005 g l‐1. Dihydrocoumarin showed highly efficient inhibition of root and shoot growth in barnyardgrass at low concentrations compared with coumarin. These findings show that weeds may be used as cover crops to provide allelochemicals for weed suppression and that dihydrocoumarin has the potential to be used as a bioherbicide. [ABSTRACT FROM AUTHOR]