Plum Pox

Plum pox is one of the most destructive diseases of stone fruits and I hope you never, ever see it.

Plum pox in apricot (John Hammond) Public Domain

This viral disease affects almond, apricot, cherry, nectarine, peach, plum, and prune trees, as well as some ornamental Prunus species. In 2014, it was estimated that plum pox has cost Europe over  $13 billion in crop losses. 


Plum pox originated in Bulgaria and is found in many parts of Canada, Chile, Europe, India, the Middle East, and North Africa. Plum pox was found in a Pennsylvania orchard in 1999. Less than one year later, the U.S. Department of Agriculture declared an “extraordinary emergency” which gave them the funds necessary to remove and destroy infected and exposed trees. Then, in 2006, it appeared again, but this time in Michigan and New York. The single affected Michigan tree was removed and extreme eradication efforts took place in New York. Plum pox is considered eradicated in that state, as well as in New York. For now.


These eradication efforts have cost over $65 million and resulted in the almost complete destruction of the Pennsylvania stone fruit industry. The threat posed by this disease is that severe.


​Plum pox symptoms

There are multiple strains of the plum pox virus, but the results are always unfortunate for stone fruit trees. Identifying this disease can be tricky. In some cases, the symptoms can be very subtle. They can vary by virus strain and host cultivar.  Generally speaking, leaf veins turn yellow and light green or yellow rings may appear on leaves, fruits, and pits. These symptoms may disappear during the heat of summer, only to return in autumn. Leaves may also exhibit crinkling, curling, and puckering. Cultivars with large, showy flowers may become variegated. Fruit may be deformed, turn brown, or develop concentric colored rings. premature fruit drop may also occur.


Unfortunately, these symptoms do not usually appear until the infection has been present for 2 or 3 years. During this time, several other nearby trees can easily become infected.


Plum pox transmission

The plum pox virus can travel long distances on infected plant material and insects. Grafting infected scions can transfer the infection to healthy trees. Several aphid species can carry this virus. 


How to avoid plum pox

If you only buy certified disease-free bare root stock and other fruit and nut trees, odds are pretty good that plum pox will not find your garden {assuming you don’t live where plum pox is already a problem). Placing new plants in quarantine and doing the best you can to control aphids will also help prevent this disease. Efforts are underway to develop resistant cultivars, but those trees are not yet available.


Plum pox may not kill fruit trees, but it can reduce production so much that you will probably end up replacing the trees anyway. Infected trees often produce fruit that is misshapen and more acidic than healthy fruits.


If you suspect plum pox, please contact your local County Extension Office or Department of Agriculture immediately.