Relatively rapid, highly specific monoclonal antibody‐based enzyme‐linked immunosorbent and immunofluorescent assays have been developed to detect and visualizeNectria galligenain woody tissue. Hybridoma cell lines were raised by co‐immunization of mice with extracts from freeze‐dried cultures ofN. galligenaand murine polyclonal antiserum to a related pathogen,N. haematococca.This method appeared to reduce the number of hybridoma cell lines that secreted cross‐reactive antibodies. From two fusions, ten cell lines that recognizedN. galligenaand notN. cinnabarinawere raised. Hybridoma supernatants were screened by ELISA using antigen‐coated wells. Monoclonal antibodies from one cell line, NG‐IE4, proved useful in the detection of the pathogen in woody tissue by ELISA and antibodies from another cell line, NG‐DF11, have been used to immunolocalize the fungus in woody tissue by immunofluorescence. Further applicati