SUBJECT:                  Confirmation of Plum Pox Virus in Pennsylvania

 TO:                  STATE AND TERRITORY AGRICULTURAL REGULATORY OFFICIALS

 On October 13, 1999 scientists from PPQ, ARS, and the Pennsylvania Department of Agriculture (PDA), determined that there was now sufficient information to conclude that the virus recently detected on peaches in Pennsylvania was in fact plum pox virus (PPV).  The identification was based on the use of a number of techniques, including several different ELISA tests and IC-PCR.  The strain of the virus present in Pennsylvania has been identified as the D strain.  This strain is present in western Europe and is described as being less aggressive than some other strains (including a reduced ability to be transmitted by aphid vectors) and known to not be seed transmitted.

 PPV is a serious disease infecting stone fruit species including peaches, apricots, almonds, and plums.  Cherries are not believed to be susceptible to most strains of PPV.  Fruit from infected trees may be blemished (typically with ringspot symptoms) or deformed and frequently drops prematurely from the tree.  The disease is spread over short distances via nonpersistent aphid transmission and over larger distances through the movement of infected budwood or nursery stock.  Normal movement of people and equipment from infested orchards is not thought to play a role in the spread of the disease.

 The property at which the infestation was discovered is a 13.5 acre peach orchard located near York Springs (Adams County).  First evidence of the disease was on fruit with typical ringspot symptoms.  When the orchard was subsequently inspected, ringspot symptoms were also found on the leaves of some trees.  APHIS has issued an emergency action notification to the orchard owner, preventing any movement of plant material from the infested property.  Inspectors from the PDA and APHIS are currently conducting delimiting surveys at groves and residential properties in the area surrounding the infested orchard.  Only one additional orchard with trees showing typical PPV symptoms has so far been identified.  Tests to confirm the presence of PPV at this property are currently underway.  In addition, APHIS inspectors are reviewing the records of the infested orchard to determine the sources of any nursery stock planted in the last several years and to determine if budwood from the orchard has been moved to any other location.

 It is likely that the identification of PPV will result in the need to conduct more extensive surveys in areas where PPV may be present, and to develop a program to certify susceptible nursery stock as being free form PPV.  APHIS is currently exploring the possibility of hosting a workshop that would include participation of scientists and regulatory officials from Europe who have experience in conducting PPV control and eradication programs.  This would provide an opportunity for Federal and State scientists and officials to apply existing expertise to the current situation in Pennsylvania.  With leaves in the infested area already turning, it is unlikely that survey operations can continue for more than another week or so.  It is anticipated that by the Spring of 2000 plans for more extensive detection surveys will be in place.

 /s/Mary S. Neal

for

 Richard L. Dunkle

Deputy Administrator

Plant Protection and Quarantine