Monoclonal antibody‐secreting cell lines were generated againstPyrenophora gramineaandPhylophthora fragariaeby various immunization techniques. The specificity of each antibody was investigated by DAS ELISA, membrane ELISA and IF. Antibodies generated againstP. fragariaewere found to be genus‐specific and could be used to detectP. fragariae‐infected strawberry roots. Antibodies developed againstP. gramineashowed marked isolate variability in twoPyrenophoraspp. The differences in isolate specificity were not consistent in all the assays investigated: antibodies reacted to some isolates by ELISA but did not detect them in other assays. An attempt was made to develop a membrane ELISA for detection of the fungi in seed material using the monoclonal antibodies that had been deve