Field studies of potato leaf roll virus spread in south-eastern Scotland, 1962–1969, in relation to aphid populations and other factors

Between 1962 and 1967 spread of potato leaf roll virus (PLRV) and the pattern of potato crop infestation by common potato aphids was investigated at sites in the counties of East Lothian, West Lothian, Midlothian and Berwickshire. Within this area aphid activity and the extent of PLRV spread varied considerably both within years and between years.
Macrosiphum euphorbiae activity as measured by the angle of colonization method was as well correlated with PLRV spread as that for Myzus persicae , and in certain years Aulacorthum solani and Aphis fabae may become common enough to have an effect. Spread was not well correlated with site altitude or with distance from the market garden area of Musselburgh, previously thought to be the main regional overwintering centre for aphids. Evidence is presented of the more general distribution of market gardening in the area which may account for these variations. Results from infector units of different sizes and bulk samples suggest, as do earlier findings, that in southern Scotland PLRV spread is mainly from sources within the crop. The practical implications for potato certification in the region are discussed.