Some species of the genusEchinochloaare troublesome weeds in rice fields. The taxonomy of this genus leads to confusion in many cases due to its great morphological diversity. Because of the differential sensitivity to the herbicide quinclorac shown byEchinochloaspp., it was necessary to assess the botanical and molecular characterization of this weed.Echinochloa colonum, E. oryzoides, andE. oryzicolawere very susceptible to quinclorac treatment; by contrast,E. crus-galliandE. hispidulashowed some degree of natural tolerance. Physiological and molecular results agreed with the botanical classification of the genusEchinochloain Flora Europea. The importance of these results is due to yield losses produced by the infestation ofEchinochloaand the need for a strategy forEchinochloamanagement depending on the distribution of theEchinochloaspecies.

A survey was made of the agrestal and rudcral fiora of southern Spain, mainly in the province of Cordoba, and a total of 941 weed species in 81 families were found in ecosystems showing severe human disturbance. The families with the highest numbers of species were Compositae, Leguminosae and Gramineae: other families like Amaranthaceae. Solanaceae and Oxalidaceae were also important because of their speciai behaviour as weeds. An assessment ofthe agricultural importance of the speeies in terms ofthe damage caused to crops showed that 36-3% could be considered rare or casual, 15-6% slightly harmful. 14-1% locally harmful, 7-3% harmful, and 266% very harmful. The richness of the flora in the different ecosystems is analysed and compared with that in other countries. Composition floristique et importance agronomique des adventiees dans le Sud de I'Espagne