In March of 2004, it was discovered that plants had been shipped from some P. ramorum-infected nurseries in California to other states. USDA-APHIS traced those shipments and the recipient nurseries and suspect plants were sampled and tested for P. ramorum. As a result of these inspections, the pathogen was found in 22 states across the nation; infected plants were subsequently destroyed. As of April 2017, P. ramorum has not been found in Illinois nor any other Midwestern state.
An Emergency Federal Order Restricting Movement of Nursery Stock from CA, OR, and WA was published on December, 21, 2004. The document lists the quarantined areas and goes further by designating entire states as regulated areas. Fourteen coastal counties in California and part of Curry county in SW Oregon are under quarantine. Within the quarantined areas P. ramorum is present, is known to be established in natural areas, and eradication measures are underway. Furthermore, ALL of CA, OR, and WA are treated as "Regulated Areas". This does not mean that these states are completely infested. However, they do serve as a buffer between known infested areas and non-infested areas. The regulations were modified in 2013 & 2014 to decrease certification requirements for non-host nurseries in the regulated states, and to increase monitoring of recently and/or recurrently positive nurseries. For more information, please see the following: http://www.suddenoakdeath.org/diagnosis-and-management/regulations/