Latex Agglutination as a Rapid Detection Assay for Spiroplasma citri. Jacqueline Fletcher, Department of Plant Pathology, Oklahoma State University, Stillwater 74078. S. A. Slack, Department of Plant Pathology, University of Wisconsin, Madison 53706. Plant Dis. 70:754-756. Accepted for publication 4 March 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-754.

The latex agglutination test (LAT) was effective in detecting the wall-less mollicute Spiroplasma citri. The minimum detection level in culture medium or turnip samples enriched with spiroplasma cells was 10⁷ cells per milliliter. Cross-reactions were not detected with corn stunt spiroplasma, honeybee spiroplasma strain AS576, or flower surface spiroplasma strain 23-6. S. citri was accurately detected in preparations of some plant species, with negative results from uninfected controls. However, false positives occurred in other uninfected plant species, especially weeds. Spiroplasmas were detected in single leafhoppers (Circulifer tenellus) as well as in groups of 3, 5, 10, 25, and 41 insects, but false positives were also detected (in about 25% of cases) with healthy leafhoppers. LAT can be used as a rapid and simple qualitative assay for detecting and identifying S. citri in culture; its application to experimental uses with infected plant or insect tissue is limited to those for which stringent controls are available.