Plum Pox Plum Pox Potyvirus, D Strain First discovered in the U.S. in Adams County, PA in 1999; this viral disease of stone fruit disfigures fruit and kills the host tree. Additional Resources MISC Invader of the Month press release. May 2004 Plum Pox Potyvirus Disease of Stone Fruits. American Phytopathological Society USDA APHIS Penn State Cooperative Extension