Barley yellow dwarf virus infectivity of cereal aphids trapped at two sites in Victoria

Alate cereal aphids, Rhopalosiphum padi, R, maidis and Macrosiphum miscanthi avenae, caught in suction traps at Horsham and Burnley for two successive years (1977-78), were tested individually for infectivity with barley yellow dwarf virus (BYDV). R. padi was most numerous, making up 73.1-98.7 % of the total number of cereal aphids trapped at either site in either year. 22.6-61.3 % of R. padi caught were infective, with a larger proportion infective at Horsham than at Burnley in both years. 9.4.43-5 % of M. miscanthi avenae were infective, but there was little difference in the proportion infective between sites. R. maidis were trapped only at Burnley, and only in 1978 were they infective, when 7.8 % transmitted BYDV to test plants. Seasonal variation in the catches of R. padi differed at the two sites. At Horsham most aphids were trapped from August to October, whereas at Burnley most were caught from March to November.