Technical Abstract: Biological indexing for the detection of graft transmissible diseases of citrus is essential for maintaining a citrus certification program. Many of the graft transmissible diseases of citrus are harbored as latent infections in the scions, but when propagated on a susceptible rootstock that allows expression of the symptoms in the whole tree, the results are devastating. The requirements for growing plants used for biological indexing, and the indicator plants commonly used for the detection of common graft transmissible diseases of citrus will be reviewed.