I have 200 isolate of Fungi and each isolate has 6 repetitions of different concentrations of fungicide. I want to calculate EC50 for all samples

Please familiarize your self with our guidelines here #meta:faq, you are supposed to make this kind of questions providing a propper REPRoducible EXample (reprex) that includes sample data on a copy/paste friendly format, for example, this would be your sample data on such a format.

sample_df <- data.frame(
    exper = c(2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 5, 5, 5, 5, 5, 5),
    conc = c(0, 0.001, 0.01, 0.1, 1, 10, 0, 0.001, 0.01, 0.1, 1, 10, 0,
             0.001, 0.01, 0.1, 1, 10),
    effect = c(66.92166667, 66.92166667, 69.33666667, 69.30833333,
               24.66666667, 0, 60.78666667, 50.81333333, 57.70833333,
               49.67333333, 0, 0, 67.89166667, 59.64166667, 74.26333333, 73.735,
               13.85333333, 0)
)