This study aimed to control tomato welt disease caused 
by Fusarium oxysporum using Streptomyces rochei which 
known to have high antagonistic activity against the plant 
pathogenic fungi. Since presence of actinophages in the soil 
can reduce the density of such antagonistic microorganism 
(i.e. S. rochei) it was of a particular interest to prepare S.
rochei inoculum in actinophage resistant forms. Therefore, a 
spontaneous phage resistant mutant of S. rochei was 
successfully isolated. Moreover, S. rochei inoculum was 
prepared in alginate immobilized form. The obtained results 
indicated that tomato plants that were inoculated with S. rochei
free cells and Fusarium oxysporum showed moderate resistance 
to welt disease. The percentage of infection increased when 
treated with S. rochei free cells and actinophages. Immobilized 
cells of S. rochei significantly decreased the disease severity of 
infected plants, even in presence of actinophages. Furthermore, 
inoculation with actinophage-resistant mutant of S. rochei in 
presence of actinophage can protect plants and reduce welt 
disease symptoms. Results in this study revealed that the 
depressive effect of the actinophages can be avoided by 
application of S. rochei inoculum in the form of alginate 
immobilized cells. Moreover, isolation of phage resistant mutants 
of such desired bacteria can be used as well to avoid the phage 
attack. Therefore, application of immobilized cells or phage 
resistant mutants of these desired bacteria as a biological control 
agent against pathogenic fungi is highly recommended to avoid 
the phage attack and to promote the efficiencies and maintenance 
of this microorganism in the soil.