Stubborn disease of citrus, caused by Spiroplasma citri, is an important disease of citrus in the hot, arid inland areas of California and Arizona. The two methods most commonly used for detection of stubborn have been biological indexing and culture in a cell-free medium. Indexing for stubborn disease of citrus is difficult since it requires the somewhat tricky side-graft or leaf vein method, and it takes several months to obtain results. Culturing is also somewhat time consuming, sometimes requires several attempts, and can produce false positives from contamination. Culturing is the test of record for CDFA and most regulatory agencies.