Virulence of Purpureocillium lilacinum strain ZJPL08 and efficacy of a wettable powder formulation against the Asian citrus psyllid (Diaphorina citri)

Abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama, is one of the most destructive pests of citrus and the primary vector of Candidatus Liberibacter spp., which cause citrus Huanglongbing (HLB). Microbial insecticides based on entomopathogenic fungi are safer alternatives to chemical pesticides. They can mitigate the spread of HLB by suppressing D. citri populations in citrus groves. Purpureocillium lilacinum strain ZJPL08, previously isolated from D. citri cadavers, is highly pathogenic to D. citri. We determined the virulence of strain ZJPL08 conidial suspensions and the efficacy of a wettable powder formulation. The LC50 of strain ZJPL08 against D. citri at 7 d post-inoculation was 2.11 × 104 conidia/mL, and the LT50 of a 1.0 × 108 conidia/mL suspension was 3.14 d in the laboratory. Under the same conditions, the LC50 of the wettable powder was 1.39 × 104 conidia/mL, and the LT50 was 2.64 d. The corrected mortality caused by the 1500-times diluted solutions of strain ZJPL08 wettable powder in D. citri reached 86.67% at 7 d post-treatment and 100% at 14 d post-treatment under field conditions. Our study revealed that strain ZJPL08 infected D. citri by hyphae penetrating directly through the cuticle and into the body cavity and tissues. These findings show that P. lilacinum strain ZJPL08 has potential for the effective control of D. citri.