During summer and early autumn in 1989, barley yellow dwarf viruses (BYDV) were detected by ELISA in grasses collected at 72 sites in the south-west of Western Australia. Most of the grasses sampled survived the dry conditions in roadside ditches or at the edges of creeks. BYDV was found at ten or more sites in each of five perennial species, Cynodon dactylon, Ehrharta calycina, Eragrostis curvula, Paspalurn dilatatum and Pennisetum clandestinum, and in one summer annual, Digitaria sanguinalis. PAV and RPV were detected at 71% and 86% of infected sites, respectively. During the late winter and early spring in 1989, BYDV was detected in 52% of cereal crops (oats, barley and wheat) sampled in the south coastal region of Western Australia, with >5% infection being recorded in 10% of crops. Highest levels of infection within crops (up to 26%) were found in the Albany and Jerramungup districts. By contrast, the virus was found in only 29% of cereal crops sampled from the western parts of the southern wheat belt where only one crop had >2% infection. When some of the BYDV-infected cereal samples were retested, PAV and RPV were detected in 65% and 39010, respectively.