Amazonian pastures formed with Brachiaria brizantha Marandu cultivar (also known as 'Braquiarão') have been devastated by a new disease since 1995, whose typical symptoms are diseased plants dispersed in pastures. Four Pythium and one Rhizoctonia isolates were recovered from plants in the early stages of infection and infected seeds,. The results of the pathogenic tests showed P. periilum as the main pathogen. Inoculations of healthy plants with the pathogen alone or in mixture resulted in a high rate of disease (p<0.01) when P. periilum and R. solani were present in 'Braquiarão' plant tissues, showing that both pathogens are associated. This is the first report of P. periilum as the primary agent of collar rot on B. brizantha.
grass disease; Pythium periilum; Rhizoctonia solani; new disease report; palisade grass
