The EIA method uses antibodies to identify the presence of proteins or carbohydrates unique to Phytophthora. The EIA method can serve as a low-cost alternate pre-screen before PCR analysis. Samples are taken from symptomatic leaves and placed in sample tubes along with a small glass bead.

A tissue homogenizer is used to rapidly agitate the sample tube and the glass bead mascerates the leaf tissue (think of a tiny paint shaker). An extraction solution is added to leach out the plant sap. The liquid exudate is centrifuged and stored frozen for later analysis.

The commecially available assay uses a microtiter plate formatted DAS ELISA protocol to detect the presence of Phytophthora antigens. User's Guide. An enzyme substrate changes color when Phytophthora is present in the sample. The results may be observed by eye or quantified with an optical plate reader. Manufacturer's Page.