Virtual
Orchard
October 13, 1999
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