I have just got a response from Corvallis on the diseased pear trees that they still distribute anyway.
He told me that in such a case of scion being distributed anyway it’s because there’s no risk to other pear trees, diseases that after the initial infection the rapid reproduction of virus cells then cease. Unlike fig trees, berries and stone fruits there are no insects around to spread these common pear and common apple diseases, and these allowed diseases can not be spread any other way besides insects. It would take insects that do not exist (at least in the USA, lets hope that nothing exists outside the USA) to start the rapid reproduction of virus cells again.
“Fruit tree material arriving from out of the country is subject to quarantine, and is cleaned up prior to release.” - Joseph Postman
“there are common “latent” viruses in most older fruit trees.” - Joseph Postman
“We don’t restrict distribution of material from the Germplasm Repository that is infected with common domestic viruses, but we do try to alert recipients when we know that viruses are present.” - Joseph Postman
“Historic varieties are almost all infected with one or more viruses, but in apples and pears they rarely produce symptoms” - Joseph Postman
@clarkinks the quarantine that you spoke of is over because it was a false alarm:
“Oregon imposed a quarantine on movement of certain plant materials because there were some positive tests for the bacteria Xylella fastidiosa from several pear trees in our collection in late 2015. Those tests turned out to be false positives and we have resumed distribution of scionwood.” - Joseph Postman