The isolation results of iris plants infected with wilt and bulbs rot showed the presence of Fusarium oxysporium which is considered the first record of the fungus on iris plants in Iraq for there is no previous indication of iris infection with this fungus. The results of the pathogenicity potentiality of Fusarium oxysporium show the occurrence of wilt and rot for the bulbs of the Iris hollandica. The biological control in vitro on the growth of the fungal revealed that the biological agent Trichoderma viride was the best in reduction of mycelium growth which caused fungal inhibition reached to 95.65%. While, the results of the biological control show controlling the infection of the inoculated bulbs, the biological agent Bacillus subtillis has the superiority in growing and developing the infection on the inoculated bulbs in an exposure period of (60) minutes. So, the mean of the spot diameter is (2.12)mm. While the biological factors does not differ significantly from each other in the spot diameter mean. Throughout studying the effect of the the biological factors on the features of plant growth, the treatment with the biological factor T. harziantum and T. viride showed a superiority in imp- roving the features of the growth of iris plants as compared with the other treatments, and the use of these biological factors with the dipping method shows a significant superiority from the soil drench method in improving the growth features of iris plants.