Weeds are one of the main problems causing losses in agricultural crops, which are nowadays mainly combated by the massive use of chemical herbicides. The development of new effective, sustainable, environmentally and health-friendly bioherbicides is a fundamental need worldwide. In this work, hydrolates and lavandin distilled straws produced during the distillation of the essential oil of lavandin (Lavandula x intermedia) were tested as potential bioherbicides. The weeds used were brome, annual ryegrass (monocotyledons), goosefoot and mat amaranth (dicotyledons) and the crops wheat, barley (monocotyledons), lentil and vetch (dicotyledons). The herbicidal capacity of both by-products was studied by applying the hydrolates in vitro on seeds and mixing the distillation straws with the growing substrate. Lavandin hydrolates significantly inhibited germination and growth of the four weeds used, being also phytotoxic for monocotyledonous crops, but hardly showed a phytotoxic effect on the dicotyledonous crops (lentil and vetch). With respect to lavandin distilled straws, they had an allelopathic effect of growth inhibition on all weeds and crops used in the work. In both by-products, lysophosphatidylcholine was identified as one of the major metabolites, while coumaroyl hexoside and feruloyl hexoside were identified as major metabolites only present in the straws. So far, only the phytotoxic capacity of the metabolites lysophosphatidylcholine and coumaroyl hexoside had been described. Therefore, byproducts from the industrial distillation of lavandin could be used in the development of effective and sustainable bioherbicides, due to the allelopathic capacity of the metabolites present.
