| Summary: | Entomopathogenic fungi are commonly applied as inundative sprays to protect plants against insect pests. Their artificial establishment as fungal endophytes to provide other benefits to the host plants aside mere protection against the primary pests has also been widely demonstrated. In the present study, two fungal strains of <i>Beauveria</i> <i>bassiana</i> and one strain of <i>Isaria fumosorosea</i> were assessed in a pathogenicity test against adults of Asian citrus psyllid (<i>Diaphorina citri</i>) and found to induce 50% reduction in the survival rate of <i>D. citri</i> adults within 5 days of exposure. The ability of the three fungal strains to endophytically colonize <i>Citrus limon</i>, the impact on plant growth and the effects of systemic colonization on 3 successive generations of <i>D. citri</i> feeding on colonized plants was evaluated. Citrus seedlings at 4 months post-planting were inoculated with each of the fungal strains via foliar spraying. Both strains of <i>B. bassiana</i> successfully colonized the seedlings. One of the <i>B.</i> <i>bassiana</i> strains (BB Fafu-13) was sustained up to 12 weeks in the colonized seedlings, whereas the other <i>B. bassiana</i> strain (BB Fafu-16) was only recovered up to 8 weeks post-inoculation. <i>Isaria</i> <i>fumosorosea</i> (IF Fafu-1) failed to colonize the plant. Both strains of <i>B. bassiana</i> induced significant improvement in plant height and flush production in endophytically colonized seedlings. In addition, endophytic <i>B. bassiana</i> caused 10−15% <i>D. citri</i> adult mortality within 7 days of exposure. Female <i>D. citri</i> feeding on <i>B. bassiana</i> challenged plants laid fewer eggs as compared to those feeding on endophyte-free seedlings, while reduction in adult emergence was recorded on <i>B. bassiana</i> treated plants. With this study, we present the first evidence of <i>B.</i> <i>bassiana</i> artificial establishment as fungal endophyte in citrus plants and its negative effects on <i>D. citri</i>.
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