Cereal aphid flights and barley yellow dwarf virus infection of cereals in Canterbury, New Zealand

Abstract Weekly catches of six aphid species known to be vectors of barley yellow dwarf virus (BYDV) were recorded in a suction trap at Lincoln, Canterbury, New Zealand. Total catches for the April‐July period in 1983–91 were 2847 Rhopalosiphum padi , 512 R. maidis , 21 R. insertum , 234 Metopolophium dirhodum , 1 M. festucae , and 24 Sitobion fragariae . Flight activity extended into June and July, when seedling winter cereals had emerged, in 1985, 1987, and 1990. Estimates of spring BYDV infection rates in Canterbury were <1% in 85% of 712 cereal crops surveyed in 1983–91, and infection rates >5% occurred in 6% of all crops, in 1985, 1986, 1987, and 1990. There was a significant ( P < 0.01) linear relationship between log 10 numbers of aphid vectors trapped in June–July and the proportion of crops (logits) with >5% BYDV in late spring. Factors affecting this relationship are discussed.