Plum Pox Virus Conference Update

The international conference, Understanding and Preparing for the Threat of Plum Pox Virus Spreading to California and the Western States, was held on the UC Davis campus on September 29-30 2014, organized by the Fruit & Nut Research and Information Center.

Invited presenters included experts from regions affected by PPV worldwide and researchers investigating the effects of PPV on stone fruit species. They addressed the biology of the disease, its current status world-wide, and development of measures to manage the disease in California. We are maintaining the conference website to provide links to video recordings and some abstracts of conference presentations. Conference website: http://ucanr.edu/sites/plumpox2014.

It is our hope that the conference provided useful information concerning the threat posed by PPV to California stone fruit growers and facilitated awareness of educational and extension tools available to the stone fruit industry.

Our thanks to Gary Obenauf (Research Director of the California Dried Plum Board) for providing the following detailed summary of the  impact of PPV on the stone-fruit industry worldwide, and its threat to that industry in California:

The U.S. stone-fruit industry is under threat from Plum pox virus (PPV) (aka sharka disease). This exotic invasive pathogen, spread by aphids, compromises tree health, causes premature fruit drop and reduces fruit quality. First identified in Europe in the early 20th century, PPV has rapidly spread world-wide since the late 1980s. PPV is now present in all major fruit growing countries except the U.S., Australia, New Zealand, and South Africa. Current losses in Europe, where the virus is most prevalent, amount to $180 million each year. Virus control consists of tree removal. The U.S. is highly vulnerable to this disease with few resistant cultivars and few resistant germplasm resources.

In 1999 PPV was detected in Pennsylvania. After 10 years and the almost complete destruction of the Pennsylvania stone fruit industry, the virus was declared eradicated in that state. PPV was detected in Ontario Canada in 2000. Almost 275,000 stone fruit trees were destroyed in a 10 year eradication effort. In 2012 Canadian officials terminated the eradication program and embarked on a PPV monitoring and management program (Canadian Food Inspection Agency). The presence of PPV in Ontario is a persistent threat to the U.S. stone fruit industry. In the summer of 2006, a national surveillance program detected PPV outbreaks in the states of New York and Michigan. It has since been eradicated in Michigan and appears to be eradicated in New York. If infected propagation materials or the virus were to reach California, the results could be devastating. California currently grows approximately 973,800 acres of susceptible stone fruits (USDA). Unlike Pennsylvania, the California stone fruit industry is characterized by very large commercial orchards grown in close proximity under ideal environmental conditions for aphid and virus spread. The stone fruit industry in the U.S. is valued at $1.8 billion annually. PPV has the potential to curtail fruit production anywhere from 10-100%, depending on the level of cultivar susceptibility.