Rice blast caused byPyricularia oryzaeoccurs on wheat under natural field conditions in Brazil. Isolates ofP. oryzaecollected from rice, wheat and grass weedsDigitaria sanguinalis, Rhynchelytrum roseum, Pennisetum setosumandEleusine indicawere tested for virulence to 30 rice, five wheat and one barley cultivars. All isolates from rice, wheat and grass weeds were pathogenic to the wheat cultivars and barley. However, none of the 10 wheat and seven grass isolates infected any of the 30 rice cultivars.