Leafhoppers are the only known vectors of X-disease phytoplasma.

Seven leafhoppers are known to 
transmit X-disease phytoplasma:

Colladonus geminatus
Colladonus montanus reductus
 Euscelidius variegatus
Fiebriella florii
Paraphlepsius irroratus
 Scaphytopius acutus 

The two most common leafhoppers in Washington are C. montanus reductus and C. geminatus.