Potent herbicidal activity of Inula crithmoides L.

Aqueous (10, 20, 30 and 40 g/L) and organic (hexane, chloroform and methanol, at 3000 and 6000 ppm) extracts of Inula crithmoides L (roots, stems, leaves and flowers) were evaluated for their allelopathic activities on radish, lettuce, peganum and thistle. Pot cultures were conducted by incorporation of I. crithmoides leaves and flowers powder (1.25 and 2.5 g/kg) in soil and by irrigation with their aqueous extracts at 40 g/L. PEG (polyethylene glycol) solutions, with similar osmotic potentials of aqueous extracts, at the highest concentration, were without effect on target species, this eliminates the extracts osmotic effect. Germination index was not affected by root and stem extracts and significantly decreased by the two other ones. For growth, leaf and flower extracts had the most significant toxicity at 40 g/L, inducing up to a total inhibition. For organic extracts, a strong toxicity was recorded for the three fractions at 6000 ppm, thistle seedling growth was more sensitive, especially to chloroform fractions. Soil incorporation of residues (at 2.5 g/kg) significantly decreased root (35-100%) and shoot (0-100%) length of target species. Irrigation soil with leaves and flower aqueous extracts was harmful for peganum and thistle, respective inhibition percentages were 100% and 66.5%. I. crithmoides may be favorably used for incorporating in agricultural systems for sustainable weed management. (C) 2011 Elsevier B.V. All rights reserved.