The biocontrol effects of Beauveria bassiana and Isaria fumosorosea on Asian citrus psyllid

Objective To study pathogenicity and biological control effects of two entomopathogenic fungi Beauveria bassiana and Isaria fumosorosea to the nymphs and adults of Asian citrus psyllid (ACP) Diaphorina citri.

Method The spore suspensions of B. bassiana and I. fumosorosea were diluted to 1×10⁴, 1×10⁵, 1×10⁶, 1×10⁷ and 1×10⁸ mL^-1, and then were sprayed on ACP younger instar, older instar nymphs and adults indoor to study the lethal effects and under semi-field conditions to study the control effects against ACP adult population.

Result B. bassiana and I. fumosorosea had higher pathogenicity to younger nymphs (2-3 instar) than to older nymphs(4-5 instar). After seven days infection, the LC₅₀ of B. bassiana and I. fumosorosea to ACP older nymphs were 3.6×10⁴ and 5.2×10⁴ mL^-1, to ACP younger nymphs were 3.5×10⁴ and 4.2×10⁴ mL^-1, and to ACP adults were 1.4×10⁵ and 1.6×10⁵ mL^-1 respectively. Under semi-field conditions, the LC₅₀ of B. bassiana and I. fumosorosea to ACP adults increased to 3.7×10⁵ and 1.2×10⁶ mL^-1. The lethal effects of two fungi at the same spore concentration against ACP in semi-field were lower than those indoor. Meanwhile, the lethal time of both fungi to ACP adults was correlated with spore concentration. The LT₅₀ decreased with the increase of spore concentration, ranged between 5.2-4.4 days when the spore concentration of B. bassiana varied from 1×10⁵ to 1×10⁸ mL^-1, and ranged between 5.3-4.9 days when the spore concentration of I. fumosorosea varied from 1×10⁶ to 1×10⁸ mL^-1.

Conclusion Both B. bassiana and I. fumosorosea have good biocontrol effects against ACP. The fatality rates of ACP are positively correlated with the concentrations of fungal spores.