The relation between aphid flights and the spread of potato virus YN (PVYN) in the Netherlands

Summary In the Netherlands early haulm destruction is the main method of preventing excessive spread of virus diseases in seed potato crops. When potato leaf roll virus was the principal problem, the time of haulm destruction was determined by the flight ofMyzus persicae (Sulzer), studied with the aid of Moericke yellow water traps. As potato virus Y^N became a problem and other aphid species interfered, the interpretation of aphid flights became difficult. An attempt is made to quantify total aphid flight activity in terms of risk to the crop. By attributing relative efficiency factors to 9 vector species and considering their flights as recorded with suction traps, values of vector-pressure are obtained that correlate well with weekly infection of bait plants. If accumulated vector pressures are compared with the flights ofM. persicae as recorded with Moericke traps during 1970–1979, it appears that during 6 of these years the critical periods of both systems coincide. However, in 1974 and 1976 much potential vector threat occurred before the start of the flight ofM. persicae. Suggestions are made as to how to apply the method in practice. A semi-popular account of this paper has appeared in Dutch inGewasbescherming 12 (1981) 57–71.