The EC method for the detection of latent ring‐rot infections (Corynebacterium sepedonicum) consists essentially of an indirect immunofluorescence test and a pathogenicity test on eggplant (EP). When interpreting the results of this method, care should be taken that: (a) eggplants are grown at 21°C. At 28–29°C the detection level of the EP was increased 102to 103‐fold to 105to 106cells ml‐1and latent infections (which may go unnoticed) occurred with 104to 105cells ml‐1; (b) reisolations are made from symptomless eggplants grown at the optimum temperature (21°C) as latent infections can also occur in these plants at concentrations of 102to 103cells ml‐1; (c) potato tuber extracts are tested without freezing or stored freeze‐dried or in a proper protective agent. Freezing at ‐20°C in maceration buffer of cells ofC. sepedonicumandPseudomonas solanacearum(the latter was included for comparison) reduced their numbers by 90–98% after one day. This could easily cause viable cell numbers to drop below the detection level of t