APHIS Factsheet

Plant Protection and Quarantine June 2012

Plum Pox

Plum pox potyvirus (PPV), also known as sharka, is 

the most devastating viral disease of stone fruit worldwide. PPV severely reduces fruit yield and quality, 

rendering fruit that is blemished and unmarketable. 

Stone fruit species—or members of the genus 

Prunus—that are susceptible to plum pox include 

almonds, apricots, cherries, nectarines, peaches, and 

plums, among others. PPV can also infect wild and 

ornamental Prunus varieties, such as Korean cherry 

(a.k.a., fl owering almond or oriental bush cherry), 

black cherry (a.k.a., rum cherry or mountain black 

cherry), and American wild plum. 

There are six known strains of PPV: D, M, EA, C, W, and 

PPV-Rec (Recombinant). The most widely distributed 

strains of plum pox are PPV-D and PPV-M. And, while 

both of these strains can infect peach, nectarine, plum, 

and apricot, M is much more aggressive in peach and 

spreads rapidly in orchards via aphids. PPV-M is also 

the only strain reported to transmit the virus through 

seed. To date, PPV-D is the only strain detected in the 

United States.

History of the Plum Pox Virus

First described on plums in Bulgaria in 1915, PPV 

has spread throughout Europe, the Mediterranean, 

the Middle East (Egypt and Syria), India, and Chile. 

In Europe, PPV has infected more than 100 million 

stone fruit trees. The fi rst documented case of plum 

pox in North America was detected in a Pennsylvania 

orchard in 1999. The following year, Canadian officials 

detected PPV in Ontario. In 2006, subsequent U.S. 

detections were made in New York and Michigan. 

The establishment and unmitigated spread of PPV in 

the United States could not only jeopardize the nearly 

$1.4 billion U.S. stone fruit industry, but also diminish 

commercial nursery production and residential stone 

fruit yields and quality, as well.

Plum Pox Symptoms

While yellow or brown blotches or rings on the leaves 

or fruit of Prunus plants are notable characteristics of 

plum pox, there are a number of other symptoms that 

may appear, including: severely deformed and bumpy 

fruit; leaf distortion and drop; and deformed, discolored 

seeds. Because infected Prunus trees exhibit such a 

wide range of leaf, fl ower, and fruit symptoms, educating 

survey crews, diagnosticians, growers, and nurserymen 

about the broad range of PPV symptoms is crucial to 

detecting plum pox.

In peach, for example, PPV-infected trees may exhibit 

color-breaking symptoms in the blossoms. This appears 

as darker pink stripes on the fl ower petals and can be 

useful for early season surveys. PPV symptoms can be 

present in young leaves in the spring and on the surface 

of developing fruit. Symptoms can persist on mature 

leaves and fruit, as well. 

Sometimes, infected trees display no symptoms on 

the leaves or fruit at all. In Chile and Pennsylvania, 

scientists discovered numerous, symptom-free orchards 

infected with PPV. Because these orchards were 

asymptomatic, scientists could not confi rm the presence 

of virus in the trees until they had conducted a battery 

of rigorous laboratory tests.

Spread of Plum Pox

Plum pox is most commonly spread over relatively 

short distances by aphids (i.e., plant lice), tiny plantfeeding insects that transmit the disease while feeding. 

Aphids serve as vectors for the virus’ spread by sucking sap from PPV-infected plants and transferring the 

virus to uninfected plants. At least 20 different aphid 

species (including Myzus persicae, Aphis spiraecola, 

A. gossypii, and A. fabae) can transmit PPV throughout an orchard and to other trees in nearby orchards, 

forests, and residential areas. Long-distance spread 

of PPV typically results from moving infected nursery 

stock or propagative materials.

While several aphid species can spread the virus, not 

all of the PPV variants can be transmitted by aphids. 

The successful transmission of the PPV also depends 

on the length of time the virus remains viable on an 

aphid’s mouthparts.

Control

Control and prevention measures for PPV include fi eld 

surveys (delimiting and detecting); use of only diseasefree (certifi ed) nursery materials and virus-resistant 

plants; control of aphid populations; and the removal 

of nurseries, orchards, and host plants in residential 

areas that are infected with plum pox.

Sources of resistance exist in Prunus but are not abundant. A team of U.S. and French scientists genetically 

engineered a PPV-resistant plum (referred to as C5) that, 

through hybridization, has been shown to transfer its 

PPV resistance to other plum trees. This PPV-resistant 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture

USDA is an equal opportunity provider and employer. 

plum is now known as the cultivar Honey Sweet. The 

U.S. Department of Agriculture’s (USDA) Animal and 

Plant Health Inspection Service (APHIS) deregulated 

this cultivar in 2007. Honey Sweet plum now provides 

a unique source of germplasm for future breeding 

programs worldwide. Scientists have yet to achieve 

similar success in attempts to breed PPV resistance 

into other Prunus species.

Economic Importance of Plum Pox

Plum pox is economically important because it causes 

fruit to be unmarketable and it weakens infected trees 

and decreases fruit yield. The presence of PPV can 

also enhance the damaging effects and increase the 

economic losses caused by other endemic viruses 

infecting various species of the genus Prunus. These 

include the prune dwarf virus, Prunus necrotic ringspot 

virus (causes browning), and apple chlorotic leaf spot 

virus (causes yellowing). 

In southeastern France, the newly identifi ed strain of 

PPV, PPV-Rec induces severe necrosis, resulting in 

early leaf drop and tree decline (even in the absence 

of endemic Prunus viruses). The severity of the 

disease depends on the strain of the virus present 

and the susceptibility of the infected Prunus cultivars 

(cultivated varieties of plants) and species. The results 

from a widescale outbreak of PPV could lead to a 

decrease in stone fruit exports and higher prices for 

domestic consumers.

How You Can Help

If you notice any signs of plum pox in your orchard or 

Prunus trees, fruit, or leaves, please immediately contact your county agricultural extension agent or one of 

the appropriate government agencies listed below.

For more information about plum pox, you can visit 

our Web page at www.aphis.usda.gov/plant_health/

plant_pest_info/plum_pox/index.shtml. 

Program Contacts

Lynn Evans-Goldner

National Program Manager

Phone: (301) 851-2286

Email: lynn.evans-goldner@aphis.usda.gov

Mafalda Weldon 

National Director

Plum Pox Virus Eradication Program

USDA/APHIS, Plant Protection and Quarantine

Phone: (585) 388-2700

Toll-Free: (800) 249-2363

Email: mafalda.weldon@aphis.usda.gov

New York

USDA/APHIS, Plant Protection and Quarantine 

Plum Pox Virus Eradication Program

Residential Survey Information

Phone: (716) 433-6482

Toll-Free: (800) 249-2363

New York State Department of Agriculture and Markets

Division of Plant Industry

Phone: (518) 457-2087

Toll-Free: (800) 554-4501

Pennsylvania

Pennsylvania Pathology and Virology Division

Phone: (717) 772-5222