Huanglongbing is an important citrus disease caused by the bacterium Candidatus liberibacter and transmitted by the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liividae). Psyllids are suppressed by chemical and biological controls including several entomopathogenic fungi such as Hirsutella citriformis Speare (Hypocreales: Ophiocordycipitaceae). A native strain of H. citriformis INIFAP-Hir 2 from Mexico was cultured in two substrates, rice (Oryza sativa L.) and oat (Avena sativa L.) in two types of containers (plastic and glass). The fungal strain was exposed to different concentrations of ethyl methane sulfonate to obtain mutants with improved production and germination of conidia, while maintaining virulence against the Asian citrus psyllid. Mutants were selected based on the amount of synnemata and sporulation. Four putative mutants were obtained, with 53-10 producing the most conidia in potato dextrose with 1% yeast extract, and also on oatmeal, compared with the wild strain. The mutant and wild strains killed 100 and 94.4%, respectively, of Asian citrus psyllids. Mycosis on adults was 60.5 and 73.4% by wild and mutant strains, respectively.