Three strains ofFusarium oxysporumwere tested for their antagonism toFusarium oxysporumf.sp.dianthi,two from alluvial soils of the Durance valley (Provence, FR) known to be suppressive toF.o.f. sp.melonis(strains 47 and 20 of Alabouvette) and a third from carnation growing medium, in which it spontaneously appeared (TF3). Strains 47 and 20 were introduced into perlite before planting carnations and found to have variable efficacy against fusarium wilt, according to the formulation of the inoculum. With a talc preparation, these strains gave only 15% witted plants, compared with 49% in the control. With a bran‐perlite inoculum, only strain TF3 gave better results than the control. Repeated introduction of TF3 through the season increased the incidence of disease, whereas a single treatment before planting in perlite was effective whatever the formulation (humid bran‐perlite, bran‐perlite powder, talc, liquid). However, the antagonistic activity of TF3 was not sufficient to control the disease in a naturally infested