Sweet pepper (Capsicum annuum L.) is an economically important vegetable crop. Wilt disease caused by Fusarium oxysporum f. sp. capsici is a specific pathogen that affects the pepper. Four isolates of F. oxysporum f. sp. capsici Fo3, Fo6, Fo7 and Fo8 were obtained from diseased pepper plants that were collected from different pepper fields in Baghdad. Fo6 isolate that has high pathogenicity to pepper seeds, Trichoderma harzianum (Th) was tested in vitro against F. oxysporum f. sp. capsici showed a high inhibition rate for the isolate Fo6, the concentration of chelated iron Fe-EDDHA 0.5% reduced the radial growth of Fo6 while did not affect the growth of Th. In pots experiment, the treatment Fo6+Th+Fe showed a significant reduction in the incidence and severity of root rot and wilt diseases. The treatment Th+Fe achieved a highly significant increase in fresh and dry root and vegetative weight 63.36, 130.56, 4.55 and 10.26g respectively, compared with control (without pathogenic) reaching 11.10, 54.83, 1.30 and 3.70g respectively. Moreover, in greenhouse the treatment Fo6+Th+Fe has reduced the incidence and severity of disease 3.33 and 1.67% respectively, and the treatment Th+Fe gave an increase in the total chlorophyll content 104 SPAD compared with the control 70.4 SPAD.
