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The Asian citrus psyllid (ACP), Diaphorina citri , is an important pest of citrus, which transmits the disease Huanglongbing (HLB) and has had devastating effects on the citrus industry around the world. Control relies mainly on synthetic pesticides, but biological control using entomopathogenic fungi may provide an alternative strategy. We evaluated sixteen fungal isolates in total; three of Beauveria bassiana , two of Metarhizium anisopliae , three of Isaria fumosorosea (Group 1); and eight isolates of Hirsutella citriformis (Group 2). The in vitro growth, germination (after different incubation times) and sporulation were assessed for all isolates at four temperatures: 20, 25, 30 and 35 °C. Overall, the Group 1 isolates achieved the greatest growth, germination rate and sporulation compared with the H. citriformis isolates In Group 2. Among the Group 1 isolates, B1, M2 and I1 had the greatest performance in the biological attributes evaluated. Group 2 isolates were not competitive under in vitro assessment; however, they cannot be dismissed entirely until in vivo experiments are done as this species was the most common pathogen infecting ACP in the field.

The Asian citrus psyllid, Diaphorina citri, is an important pest of citrus, which transmits the disease Huanglongbing with devastating effects on the citrus industry around the world. Control relies mainly on synthetic pesticides, but biological control using entomopathogenic fungi may provide an alternative strategy. Based on previous in vitro experiments, we selected four isolates, one from each of the species Beauveria bassiana, Metarhizium anisopliae, Isaria fumosorosea and Hirstella citriformis. With these isolates, we carried out in vivo experiments to select an isolate based on its infection ability against adult D. citri. Using only H. citriformis isolates, we evaluated the mortality in D. citri achieved using blastospores. As a potential cause of the low mortality achieved with H. citriformis, we evaluated the effect of inoculum carrier (Tween 80 or distilled water) on conidial germination. We also compared the pathogenicity of dry conidia (not suspended in 0.03% Tween 80) of H. citriformis and M. anisopliae against adult D. citri. Using conidial suspensions, all isolates caused mortalities above 80% in adult D. citri cohorts, except H. citriformis, which caused a maximum of 40% mortality. The mortality caused by blastospore suspensions of H. citriformis, were 60%. Tween 80 solution and distilled water significantly reduced the germination of H. citriformis conidia. Dry conidia of H. citriformis and M. anisopliae caused 100% mortality. Our results suggest that using a combination of biological control approaches, both inundative (using M. anisopliae or I. fumosorosea isolates in suspension) and inoculative (using H. citriformis as dry conidia in autoinoculation devices), has good biological control potential. The suitability of the combined use of these two biological control approaches for management of D. citri is discussed.