Abstract: Based on in vitro results, three isolates: T. harzianum (J1), T. harzianum (J6) and T. virens were selected for greenhouse studies. Biocontrol efficacy of these isolates as well as the combination of T. harzianum (J1) and T. virens on crown and root rot of sunflower were studied in series of experiments using three methods; incorporation of conidial suspension into the soil (107 conidia g-1 soil), incorporation of conidial suspension mixed with compost (107 conidia g-1 compost) into the soil and impregnating of sunflower seeds with conidial suspension (107 conidia mL-1). Experimental data were analyzed with Randomized Complete Block Design (RCBD) and means compared by Duncan`s multiple range test. Greenhouse experiments (in vivo) showed that, the combination of T. harzianum (J1) and T. virens using incorporation of conidial suspension mixed with compost into the soil had the most efficiency on biocontrol of S. minor and reduced disease incidence up to 50%.

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