APHIS Factsheet

Plant Protection and Quarantine October 2008

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). PPV D and M 

are the most widely distributed strains of plum pox 

worldwide. 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 plum is now known as the cultivar 

“Honey Sweet.” The Animal and Plant Health Inspection Service deregulated this cultivar in 2007. Honey 
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, 

national origin, age, disability, and where applicable, sex, marital 

status, familial status, parental status, religion, sexual orientation, 

genetic information, political beliefs, reprisal, or because all or part 

of an individual’s income is derived from any public assistance 

program. (Not all prohibited bases apply to all programs.) Persons 

with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) 

should contact USDA’s TARGET Center at (202) 720–2600 (voice 

and TDD). To fi le a complaint of discrimination, write to USDA, 

Director, Office of Civil Rights, 1400 Independence Avenue, S.W. , 

Washington , D.C. 20250–9410 , or call (800) 795–3272 (voice) or 

(202) 720–6382 (TDD). USDA is an equal opportunity provider and 

employer. 

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 wide-scale 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 http://www.aphis.usda.gov/plant_health/

plant_pest_info/plum_pox/index.shtml. 

Plum Pox Virus Eradication Program National 

Coordinator:

USDA-APHIS-PPQ

Plum Pox Virus Eradication Program

401 East Louther Street, Suite 102

Carlisle, PA 17013

Telephone: (717) 241-0705 

Toll-Free: (800) 249-2363 

Fax: (717) 241-0718

Pennsylvania:

Pennsylvania Pathology and Virology Division

Attn: Plant Lab

2301 North Cameron Street

Harrisburg, PA 17110–9408

Telephone: (717) 772-5222

Fax: (717) 705-6518 

Michigan:

USDA-APHIS-PPQ

Plum Pox Virus Eradication Program

Michigan Field Office

4032 M-139, Room 124

Saint Joseph, MI 49085

Telephone: (269) 408-0976 

Fax: (269) 408-1391 

Michigan Department of Agriculture, Region 5

4032 M-139, Room 116

Saint Joseph, MI 49085

Telephone: (269) 428-2546 

New York:

USDA-APHIS-PPQ

Plum Pox Virus Eradication Program

New York Field Office

23 Elizabeth Drive

Lockport, NY 14094

Telephone: (716) 433-6482 Ext. 200 

Fax: (716) 433-6593 

New York State Department of Agriculture and Markets

Division of Plant Industry

10-B Airline Drive

Albany, NY 12235-0001

Telephone: (518) 457-2087 

Toll-Free: (800) 554-4501