Herbicidal activity of natural compounds from Baccharis spp. on the germination and seedlings growth of Lactuca sativa and Bidens pilosa

We evaluated the effects of aqueous and ethanolic extracts from 3-Baccharis species (B. dentata, B. uncinella and B. anomala) on the germination and seedlings growth of Lactuca sativa (model specie) and Bidens pilosa (weed) and by chemical analysis determined the phenolic compounds present in extracts. Aqueous and ethanolic extracts of B. dentata, B. uncinella and B. anomala were tested at 2.5, 5, 7.5 and 10% concentrations. Allelopathic effects of three Baccharis species were variable. The B. pilosa was more sensitive to the extracts than L. sativa and germination was inhibited with ethanolic extracts of B. anomala and B. uncinella from 5 to 10%. Aqueous extract of B. dentata and B. uncinella at 10% concentration reduced the germination of B. pilosa by 80%. The ethanolic extracts of B. uncinella (2.5 to 10%) and B. anomala (5 to 10%) caused 100% mortality of seedlings. Total phenolic compounds were more abundant in aqueous extracts. Amongst the phenolics, catechin was most abundant (1.61 to 6.16 mg g-1 DM) in aqueous and ethanolic extracts of Baccharis species tested. This study showed that Baccharis uncinella may be used as an alternative bioherbicide to control the weeds in agroecosystems