A Dipstick Immunoassay for the Specific Detection ofPhytophthora cinnamomiin Soils

A dipstick immunoassay that is specific for Phytophthora cinnamomi was developed for use in soils. Azo dye detection of monoclonal antibody-labeled cysts attached to a nylon membrane provided a rapid, sensitive assay suitable for field use. There was no cross-reaction with other Phytophthora and Pythium species in controlled environment assays or with soil or other organic matter that adhered to the membrane. The assay was as sensitive as a Eucalyptus sieberi baiting assay and, when run together with the baiting assay, was quantitative for an infested soil-water suspension from 2.5 × 10 2 to 5 × 10 3 zoospores per milliliter. The assay was used successfully to detect P. cinnamomi in a wide range of soil samples collected from beneath a diverse range of host species