Boles of four Erythrobalanus oaks were inoculated with white and gray isolates of Ceratocystis fagacearum at diametrically opposed loci. Bole and branches were sampled in an orderly manner when a tree exhibited moderately severe foliar wilt symptoms. Isolations were made on PDA plates. Of the four red oaks, two yielded only the white isolate; the remaining two yielded both isolates. In no instance were both isolates recovered from the same branch, but all sections from the main trunk yielded both, and in several instances both isolates were observed growing from the same chip. This pilot experiment and the findings of other workers indicate that any factor effecting survival of one isolate of C. fagacearum over others is manifested at the time of germination of inocula, and that mycelia of different isolates have little significant inhibitory effect on each other
