Pasture for raising cattle has been the major land use in the Amazon region of Brazil. This agricultural practice has caused environmental disturbances associated with deforestation and burning. After five or six years of intensive pasture, the land undergoes degradation due to poor management and high weed infestation. A survey was carried out to identify the main weeds in 0.33 ha pastures covered with Brachiaria humidicola in Terra Alta, located at the northern region of Pará - Brazil (0º 58" S e 47º 52" W. Gr.). The 4,700 specimens were sorted out in 17 botanical families with 35 species belonging to Poaceae, Rubiaceae, Fabaceae, Asteraceae and Solanaceae, with five, five, four, three and three species being found, respectively. The most important weed species in the community were Borreria verticillata, Hyptis atrorubens, Rolandra argentea, Desmodium canum, Panicum pilosum, Davilla rugosa, Imperata brasiliensis, Paspalum maritimum, Vernonia scorpioides and Vismia guianensis.
botanical survey; Amazon region; infestation; Brachiaria humidicola
