Identification of optimal environmental conditions for growth and sporulation of biological control agents is necessary for their mass production. The response of these agents to environmental conditions differs not only among species, but also among strains. Therefore the effects of food quality, light, temperature and pH of medium on growth and sporulation of Verticillium lecanii DAOM 198499 were investigated. Results indicated that, the effect of food quality on sporulation was significant (?=0.01). Potato extract enriched with dextrose, peptone and yeast lead to higher sporulation than potato extract alone. Effect of light was not significant. Temperature above 30?C restricted blastospore production, but sporulation at 12, 17, 22, and 27?C were not significantly different (?=0.01). Blastospore production increased intensively during the first four days after inoculation, the number of blastospore/ml reaching 4.7×108. Then the rate of increase was reduced, reaching to 9.06×108 after 10 days, which was not statistically different from the 4 day, production. Effect of medium pH on sporulation was not significant. Fungus activity caused change of pH of media toward its favourite acidity. Difference of blastospore production in alternative media was significant (?=0.01). Comparison of means revealed that sugar beet molasses and rough rice extract with numbers of 1.02×108 and 1.06×107 blastospores/ml had the highest and lowest rates of sporulation, respectively.
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