The allelopathic potential of Citrus junos fruit waste after juice extraction was investigated. Aqueous methanol extracts of peel, inside and seeds separated from the fruit waste inhibited the growth of the roots and shoots of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), crabgrass (Digitaria sanguinalis L.), lettuce (Lactuca sativa L.), timothy (Pheleum pratense L.), and ryegrass (Lolium multiflorum Lam.). The inhibitory activity of the peel extract was greatest and followed by that of the inside and seed extracts in all bioassays. Significant reductions in the root and shoot growth were observed as the extract concentration was increased. The concentrations of abscisic acid-beta-D-glucopyranosyl ester (ABA-GE) in eel, inside and seeds separated from the C junos fruit waste were determined, since ABA-GE was found to be one of the main growth inhibitors in C junos fruit. The concentration was greatest in the peel, followed by the inside and seeds; there was a good correspondence between these concentrations and the inhibitory activities of the extracts. This suggests that ABA-GE may also be involved in the growth inhibitory effect of C junos waste. These results suggested that C junos waste may possess allelopathic potential, and the waste may be potentially useful for weed management. (C) 2004 Elsevier Ltd. All rights reserved.