Comparison of ELISA Techniques and Standard Isolation Methods for Phytophthora Detection in Citrus Orchards in Florida and California. L. W. Timmer, University of Florida, IFAS, CREC, Lake Alfred 33850. J. A. Menge, S. E. Zitko, E. Pond, S. A. Miller, and E. L. V. Johnson. University of California, Riverside 92521; University of Florida, IFAS, CREC, Lake Alfred 33850; University of California, Riverside 92521; Agri-Diagnostics Associates, Cinnaminson, NJ 08077; and University of California, Riverside 92521. Plant Dis. 77:791-796. Accepted for publication 8 April 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0791.

Commercial enzyme-linked immunosorbent assay (ELISA) kits were evaluated for detection of Phytophthora spp. in fibrous roots and soil in citrus orchards in Florida and California, and compared to root rot evaluations, percent infection in root pieces, and dilution plating of soil on selective media. In Florida, root ELISA values with kits D and E were correlated with percent root infection and propagule densities of Phytophthora parasitica on an orchard basis. In California, root ELISA values with kit D were correlated with propagule densities of Phytophthora citrophthora on an orchard basis. Kit D was more effective than kit E for the detection of Phytophthora spp. in fibrous roots because of high background values with kit E. Soil ELISA values with kit E were not related to other measurements of Phytophthora activity. Variability of root ELISA values and propagule densities in single-core samples was of the same order of magnitude. Kit D was much less reactive to P. citrophthora hyphae than to P. parasitica. The kit D ELISA values from fibrous roots provided as effective a measure of Phytophthora activity as the currently used propagule densities from soil.