Lettuce Necrotic Yellows Virus

Abstract

A DESTRUCTIVE virus disease of lettuce, causing extensive crop losses sometimes as high as 100 per cent, was recognized in Victoria in 1954 as being distinct from the lettuce mosaic disease. Until 1959, however, all attempts to transmit the virus to lettuce with aphids which commonly infest lettuce, with thrips, leaf-hoppers and sap inoculation methods were unsuccessful. In that year a virus was transmitted mechanically to Nicotiana glutinosa L. from many diseased lettuce plants and from apparently normal common sowthistle (Sonchus oleraceus L.) plants. These isolates were, at first, incorrectly identified as mild variants of the tomato spotted wilt virus¹, because of the remarkable similarity between the diseases caused by the two viruses on some common hosts, including lettuce. The tomato spotted wilt virus has been isolated occasionally from lettuce; but it is of minor significance in Victoria, Australia, possibly because common strains found here on tomato and other hosts do not appear to infect lettuce in Nature.