Epidemiology of lettuce necrotic yellows virus in South Australia. II. Distribution of virus, host plants, and vectors

Abstract

A survey has shown that both lettuce necrotic yellows virus (LNYV) and its vector Hyperomyzus lactucae are commonly associated with the widely distributed host plant, Sonchus oleraceus. Three newly discovered naturally infected host plant species, Reichardia tingitana, Sonchus hydrophilus, and Embergeria megalocarpa, have a restricted distribution, yet their ability to support colonies of the vector shows that they are potential sources of LNYV. Both S. hydrophilus and E. megalocarpa appear to be endemic to Australasia, and the possibility that either could be the original source of LNYV is discussed. Serological relationships have been demonstrated between some isolates of LNYV. A simple and rapid method for concentrating LNYV from sap extracts for serological testing is described. Hyperomyzus carduellinus has been shown to transmit LNYV, and the distinguishing morphological characteristics of this species are described. Its geographical distribution is limited, and it was found most commonly on R. tingitana.