In submerged culture, the entomopathogenic fungus Beauveria bassiana yields submerged conidia and single-celled yeast-like form referred to as blastospores. Products based on aerial conidia of entomopathogenic fungi, produced in solid fermentation, are widely used in the biological control of agricultural pests. However, very few products are based on submerged conidia and blastospores. The virulence of submerged conidia of the fungus Beauveria bassiana has not been demonstrated against the cotton boll weevil, Anthonomus grandis, and the fall armyworm, Spodoptera frugiperda, two economically important pests in cotton and maize, respectively. Here we aimed to 1) Compare the production of submerged conidia and blastospores of six isolates of B. bassiana, 2) compare the virulence of submerged conidia, blastospores, and aerial conidia of three isolates against A. grandis and S. frugiperda and 3) to study the growth kinetics of an isolate in a 6-liter bioreactor. ESALQ2291, ESALQ3780, and ESALQ4238 produced 2 to 3 more blastospores than submerged conidia, and the production of the other isolates was similar. Blastospore yields ranged from 2.62 to 6.61 × 108 mL−1, and submerged conidia yields ranged from 1.88 to 3.92 × 108 mL−1 in culture flasks. The production phases of submerged conidia were defined in the bioreactor study, while the highest yield attained was 1.2 × 108 mL−1 after 108 h of culture. In general, blastospores and submerged conidia killed insects faster than aerial conidia for both insect species. Submerged conidia of isolate ESALQ3760 killed A. grandis adults faster than aerial conidia and blastospores of the same isolate. On the other hand, blastospores of isolate ESALQ4238 and ESALQ2291 killed S. frugiperda larvae faster than submerged and aerial conidia. This study revealed the potential of submerged conidia of B. bassiana against S. frugiperda and A. grandis, although, for most isolates, blastospore presented more significant biological parameters. This study reinforced the need to seek the proper propagule of the best isolate in developing biopesticides.