In July 2006, Michigan Department of Agriculture (MDA) inspectors detected plum pox virus (PPV), a stone fruit disease previously unknown within Michigan and detected in only one other state in the U.S. The MDA imposed quarantine on May 16, 2007, centered in southwest Michigan prohibiting the movement of susceptible stone fruit nursery stock, out of, within, and into the quarantined area of approximately 9 square miles. In addition, regulated species of susceptible nursery stock within a 7.2 mile radius (Nursery Stock Regulated Area) of the site of the original positive find could not be used to propagate new plants.
Three years (2007, 2008, and 2009) of comprehensive survey using USDA sampling protocols in commercial and homeowner plantings in southwest Michigan have revealed no additional plant material testing positive for PPV. On the basis of these tests, on September 2, 2009, MDA director Donald Koivisto declared Michigan to be plum pox-free and rescinded the state quarantine. Growers within the quarantine zone will receive an official letter from the MDA releasing them from the Emergency Action Notice.