The virus causing potato leaf roll can be recovered from the haemolymph of Myzus pefsicae, the aphid vector. Infective virus has also been separated from the bodies of infected vectors. The virus can be transmitted by an aphid after a moult, and infectivity is retained for at least 8 days; during this time the aphid is able to infect many plants. M. persicae is a much more efficient vector than Macrosiphum euphorbiae.