Lettuce necrotic yellows virus in New Zealand

Lettuce necrotic yellows virus, found in lettuce (Lactuca saliva L.) and sowthistle (Sonchus oleraceus L.) near Blenheim in 1965 caused severe losses in an Auckland lettuce crop in 1969. The virus was transmitted between S. oleraceus plants by the aphid Hyperomyzus lactucae L., which occurs throughout the year but is least plentiful during winter. Most infectivity in sap extracts was lost after 8 hr, but was still detectable after 16 hr. Thermal inactivation occurred after 10 min at between 50° and 55°c, and infectivity was lost at a dilution between 1 in 100 and 1 in 500. The bullet-shaped virus particles had a sedimentation coefficient of approximately 940 S.