Not known to transmit any human or animal pathogens.

Not known to vector any pathogens or other associated organisms.

"Ca. P. aurantifolia" is vectored by the leafhopper, Hishimonus phycitis, which is not known to occur in the United States. The pathogen can also be transmitted by vegetative propagation of infected plant tissues (grafting, cuttings, etc.). Asian citrus psyllid (ACP), Diaphorina citri, can also vector the phytoplasma, although less efficiently than H. phycitis. ACP is present in the United States, but those areas are quarantined to prevent the spread of citrus greening, which is vectored by ACP.

Follow instructions in Phytoplasma Sample Screening and Confirmation. If you have completed phytoplasma specific training or proficiency testing for DNA extraction and real-time PCR from S&T Plant Pathogen Confirmatory Diagnostics Laboratory (PPCDL, formerly Beltsville lab), you can screen your own phytoplasma samples. Note: You will still have to follow the protocol in the linked document for confirmations.

In key lime: Symptoms of witches' broom disease of lime (WBDL) include witches' broom (excessive production of shoots with short internodes and small, light green leaves), abnormal flowers (phyllody), stunting, and reduced fruit production. Infected trees eventually decline and collapse over 3-8 years. In some cases, trees remain asymptomatic, or they may die back or weaken over time instead of showing typical WBDL symptoms. This slow/symptom free form of the disease is likely due to unfavorable environmental conditions (extremely hot and dry or too cool).

Other citrus: Key lime is the primary host, but other citrus species may express similar symptoms when environmental conditions are favorable for disease development.

Generally, the best time to survey for phytoplasmas is summertime when symptoms are most likely to be apparent. A study in Iran found that samples taken in August had higher concentrations of "Ca. P. aurantifolia" than those taken in March or December.

Visually inspect host plants throughout the survey site for symptoms such as witches' broom, reduced flowering and fruiting, and the general decline of the tree. Collect symptomatic leaves for sample screening.

Survey for "Ca. P. aurantifolia" in key lime (preferred) or other citrus (if showing witches' broom symptoms) in commercial or residential settings 

For most phytoplasma diseases, leaves with symptoms are optimal for diagnostic testing. It is important to sample tissue from different parts of the same tree, as phytoplasmas are often unevenly distributed. Do not sample dead leaves.

Follow instructions in Phytoplasma Sample Screening and Confirmation

No phytoplasmas are associated with citrus in the continental United States as of June 2025. Citrus greening (CG), caused by "Ca. L asiaticus", is present in some areas of the United States, which are quarantined to prevent spread. CG can cause symptoms that could be confused with WBDL such as blotchy yellowing of leaves, fruit symptoms, shoot die-back, stunting, and overall decline of the tree, but does not cause witches' broom. In Puerto Rico, a phytoplasma within the pigeon pea group (16Sr IX) was associated with orange, tangerine, and lemon, causing symptoms similar to citrus greening, but not witches' broom.

In India, "Ca. P. cynodontis"-related strains (16SrXIV-A) were associated with witches' broom symptoms similar to WBDL in key lime. Multiple phytoplasmas have been associated with citrus in Asia, the Caribbean, South America, and Central America. These phytoplasmas can cause witches' broom or nonspecific symptoms such as reduced flowering, stunting, dieback, and decline. Molecular diagnostics are required to determine the pathogen when a disease associated with a phytoplasma is suspected in citrus.