Plum Pox |
|
 |
|
Background
Overview
Plum pox is a virus disease of stone fruit species (peaches, plums, etc.) that first appeared in Pennsylvania October of 1999. The plum pox virus can be carried in live nursery stock, in grafts and budwood of infected plants, and is transmitted from one plant to another by the feeding of several species of aphid. Plum pox virus does not kill infected trees, but it causes yield losses to growers and reduces the marketability of fruit.
Subsequent to its discovery in the United States, an infestation of plum pox virus was detected in Ontario and Nova Scotia, Canada. It appears that this infestation pre-dates the one in Pennsylvania. At this time there is not evidence that the two infestations are related. The strain detected in the US and Canada is the D strain from Europe which is not the most virulent of plum pox strains, and which does not appear to infect cherry species.
In March of 2000, the Secretary of Agriculture declared an emergency and an extraordinary emergency in order to prevent the spread of the virus from Adams and Cumberland Counties, Pennsylvania to the rest of the United States and to other countries. The actions allowed the department to provide the funding necessary for eradication and to pay compensation to affected growers.
Biology
Trees infected with plum pox virus show an uneven distribution of the pathogen within the tree. Symptoms of infection appear on leaves, flowers, and fruit but may vary considerably depending on the tree species or cultivar. Fruits can become distorted in shape and show characteristic ring or spot blemishing. Flowers may have streaking on the petals or pigmented ring patterns and leaves can have rings or show light green or yellow veining. (See American Phytopathological Society's image gallery).
Several aphid species can serve as vectors for the spread of plum pox virus, varying in efficiency by the species of aphid, strain of virus, and host species affected. The virus stays viable in the aphid's mouthparts for a period of approximately one hour and most aphids can generally transmit infection up to 120 meters from the initial source plant.
For more information on the virus biology, see the American Phytopathological Society's feature article.
Hosts
Plum pox occurs on Prunus species including peaches, nectarines, apricots, plums, almonds, and some ornamental Prunus cultivars.
Distribution
Plum pox virus was first reported in Bulgaria in 1915. Also known as sharka, the plum pox virus is found in Europe, the Middle East, North Africa, India, and Chile.
For the distribution of current infestation in the United States, see the maps link on this website.
Information on the Canadian program can be found at the Canadian Food Inspection Agency's website.