In order to select botanical herbicides to Bidens alba, aqueous extracts from the leaves of 12 species, which were reported with allelopathy or potential activity of weed inhibition, were used to spray Bidens alba seedlings. The results showed that all of the leaf aqueous extracts from 12 species had significant inhibition effects on the growth of Bidens alba seedlings (P<0.05) with synthetical effects (SE)≤-0.2. The inhibition strength was in order as: Eupatorium catarium>Ageratum conyzoides>Alocasia macrorrhiza>Solanum torvum>Lantana camara>Mikania micrantha>Broussonetia papyifera>Wedelia trilobata>Ipomoea triloba>Pueraria lobata>Paederia scandens>Ipomoea cairica. The 0.04 g DW mL-1 aqueous extracts from the leaves of Eupatorium catarium could cause death of Bidens alba seedlings. The aqueous extracts from the stems of Eupatorium catarium and Ageratum conyzoides also had significant inhibition effects on the growth of Bidens alba seedlings (P<0.05), but which inhibition effects were lower than those from leaves. The analysis of regression showed that Bidens alba seedling growth negatively correlated with the concentration of aqueous extracts from the leaves of Eupatorium catarium (R2>0.85). The biomass of Bidens alba significantly decreased with increasing of the concentration of aqueous extracts. It suggested that Eupatorium catarium and Ageratum conyzoides could be used as natural botanical herbicide for Bidens alba due to their low concentration effect and wide availability.
