Pear Twig Issues

Something is causing terminal growth on my Warren pear to blister; it doesn’t really act like fireblight. New growth comes out OK, but over the season it forms blisters at each bud node which spreads to cover the whole twig.

The trunk and larger branches remain unaffected.

Psylla?

They have not been documented in our area but, something was causing pear blossom blight or blast that had never been an issue here before.