What is Plum Pox?
Plum pox is caused by a virus from the genus Potyvirus. These are one of the largest groups of plant viruses. The plum pox potyvirus is the only known potyvirus known to infect stone fruit (Prunus sp.). Several aphid species can serve as carriers for plum pox virus. Among the most important species are the green peach aphid (Myzus persicae), leaf curling plum aphid (Brachycaudus helichrysi), peach leafroll aphid (Myzus varians), damson-hop aphid (Myzus humili), thistle aphid that overwinters on plums (Brachycaudus cardui) and the spirea aphid (Aphis spiraecola) as well as many less commonly found aphids. It is important to realize that some aphids such as cherry aphid (Myzus cerasi), mealy plum aphid (Hyalapterus pruni) and non-aphids such as leafhoppers (Edwardsonia plebei), lecanium scale (Lecanium corni) and plant bug (Lygus pratensis) are not capable of transmitting the virus. There have been four strains of plum pox virus (PPV) identified in the world. Those are PPV-M, PPV-EA, PPV-C, and PPV-D. The PPV-D strain is widely spread thoughout western Europe. This is the only strain found in the western hemisphere, first in Chile then in Pennsylvania, Canada, New York, and Michigan.
History of Plum Pox
Plum pox is also called Sharka. It is considered one of the most serious virus diseases of stone fruit in Europe. First disease symptoms were observed as early as 1910 in Macedonia (part of formally Yugoslavia). Growers in Bulgaria reported seeing "pox" on plums during 1915-1918. A Bulgarian researcher, Atanasoff, was the first to write about the disease and its virology in 1932. Since then the disease spead slowly until after World War II. By the mid-1980's it had spead to most of Europe (with the exception of Belgium, Switzerland and the Netherlands where it was presumably eradicated). By the late 1980's PPV had spread to Cyprus, Egypt, Syria, and India. Plum pox was first found in North America in Pennsylvania in October of 1999. It was later discovered in eastern Ontario and Nova Scotia in 2000 and western New York in early July 2006, it was also confirmed in Michigan that same time.
Current Situation in the U.S.
As of August 2007 only Michigan, Pennsylvania, and New York are the only states that have detected PPV. All three states are conducting extensive surveys and only New York has found 13 suspected samples. Michigan and Pennsylvania have yet to find any positive or suspect samples.
In Europe, there are some 100 million trees infected presenting serious economic problems. Susceptible varieties can have up to 100 percent crop loss due to diminishing quality or massive fruit drop about 10 days prior to harvest. In the United States plum pox poses a significant threat to the stone fruit industry as mainly peaches and plums are most at risk from the strain of the plum pox virus found in North America.