In apricot, leaf symptoms are similar to those in plum but are less conspicuous. In general, cultivars of each host show differential responses to infection. The virus is aphid-transmitted in a nonpersistent manner, and infection is associated with pinwheel inclusion bodies in the cytoplasm. The most important means of spread is by diseased plant material, which accounts for much of the rapid spread among and within European countries during the last 20 years. Once established, plum pox virus is extremely difficult to eradicate.
Infection is slow to become systemic and is often confined to one or two limbs of a tree.
Because symptoms can be mild or transient, considerable spread can occur from new disease foci before infections are noticed. There are, however, reports of the virus occurring naturally in sweet and sour cherries in Moldavia and Bulgaria. Control Control depends on obtaining healthy plant material, achieved in countries in Europe by certification programs. Trees are grown from tested propagation material in isolation from potential sources of disease and are inspected before distribution to growers. Recently, eight plum pox isolates were compared in controlled inoculations under standard growing conditions in a quarantine containment facility in Frederick, Maryland.