Weed plants as sources of cucumber mosaic virus

SUMMARY Severe yellowing and stunting was widespread in lettuce crops in Britain in 1968. Cucumber mosaic virus was consistently obtained from affected plants and from weeds which were prevalent in lettuce fields. Infection was most frequent in Stellaria media but also occurred, more or less commonly, in Senecio vulgaris, Urtica urens, Tripleurospermum maritimum ssp. inodorum, Capsella bursa‐pastoris, Lamium purpureum and Sonchus oleraceus. Most infected weeds were symptomless. Infected weeds were still common in January‐April 1969 and are considered to be a major overwintering source of the virus for aphid transmission to lettuce.