Abstract
The vector-virus relationships between the aphid Myzus persicae and the sugar beet yellows virus, under laboratory conditions, using sugar beets (variety U. S. 15) as the host plant, are not typically persistent in character. Like the persistent aphid-borne viruses, acquisition and inoculation require a period of hours to reach maximum efficiency, but unlike most of the recognized persistent viruses, the period of retention is relatively brief in both feeding and fasting insects. The rate of loss can be well estimated by assuming a half-life of 8 hours in feeding insects, while in fasting aphids, the half-life is shorter, perhaps near 2.5 hours. Evidence supports the suggestion that the aphid-vector virus relationships form a continuum, with beet yellows being a representative of the semi-persistent group. In experiments where the aphids had access to a persistent virus (beet yellow-net) as well as the beet yellows virus, the indications were that the 2 viruses are transmitted as independent entities.