A large number of microtiter plates are needed for mass testing of planting material for viruses in seed certification and plant quarantine. In the case of poorly equipped laboratories, problems with availability of microtiter plates have economic implications for the broad acceptance of enzyme-linked immunosorbent assay (ELISA) for e.g. seed health testing in developing countries. In this experiment the potential of an alternative, cheaper technique was investigated. A conventional indirect ELISA procedure was followed for comparison between the polystyrene solid phases of plastic Petri dishes and microtiter plates for detection of three viruses belonging to the Tobamovirus, Comovirus and Potyvirus genera. A wax pen was used to divide the inner surface of a polystyrene Petri dish into many circles or squares.