Symptoms of Plum pox virus (PPV) can be conspicuous or very subtle on stone fruit trees.  They vary in type and severity with the strain of the virus, timing of infection, cultivar, and environmental factors.  Diagnostic symptoms occur mainly on leaves and fruits in New York.  Leaf symptoms include vein yellowing or light green to yellow rings.  Foliar symptoms may develop during the cooler temperatures of spring and fall but fade during the host summer months.  Plums can exhibit acute symptoms, including chlorotic and necrotic ring patterns or blotches. Please leaves may show leaf crinkling, puckering or curling.  Apricot leaves show lighter symptoms than plum or peach.
Flowers on PPV-infected peach trees may exhibit color breaking but only on cultivars with large showy flowers.

(Left) PPV-infected plum leaves showing vein yellowing and light green to yellow rings. Photo by M. Fuchs. (Middle) PPV-infected peach cultivars with showy blossoms exhibit color breaking. (Right) Individual petals of PPV-infected peach cultivar exhibiting color breaking.

Peach fruit may develop lightly pigmented rings or line patterns that result from the convergence of several rings.  Apricot fruits may be misshapen, turn brown or become necrotic and may have rings on the surface of the seed.  Plum fruits are often deformed and have dark rings or sports and a reddish discoloration of the flesh.  Also, some plum cultivars can drop fruit prematurely.

(Left) Discolored and deformed PPV-infected plum fruits (center, bottom) in comparison to healthy plum fruits (top). (Middle) Rings on the surface of a seed of a PPV-infected apricot fruit. (Right) PPV-infected apricot fruit with lightly pigmented rings.

Symptoms of PPV occur sporadically and often are not apparent until three or more years after infection.  Newly infected trees are rarely symptomatic.  It is critical that symptomless trees be regarded very seriously as they will act as a silent virus source for further infections.
PPV is the most widespread disease of stone fruits in Europe. This virus reduces fruit yield and quality.  It also shortens the productive lifespan of orchards and can render stone fruit trees useless for fruit production.  Even symptomless trees produce reduced quantities of fruit.  The economic impact of PPV to the peach, plum and apricot industry worldwide is estimated to $600 million per year.