Virulence ofPurpureocillium lilacinumstrain ZJPL08 and efficacy of a wettable powder formulation against the Asian citrus psyllid (Diaphorina citri)

The Asian citrus psyllid,Diaphorina citriKuwayama, is one of the most destructive pests of citrus and the primary vector ofCandidatusLiberibacter 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 suppressingD. citripopulations in citrus groves.Purpureocillium lilacinumstrain ZJPL08, previously isolated fromD.citricadavers, is highly pathogenic toD.citri. We determined the virulence of strain ZJPL08 conidial suspensions and the efficacy of a wettable powder formulation. The LC(50)of strain ZJPL08 againstD.citriat 7 d post-inoculation was 2.11 x 10(4)conidia/mL, and the LT(50)of a 1.0 x 10(8)conidia/mL suspension was 3.14 d in the laboratory. Under the same conditions, the LC(50)of the wettable powder was 1.39 x 10(4)conidia/mL, and the LT(50)was 2.64 d. The corrected mortality caused by the 1500-times diluted solutions of strain ZJPL08 wettable powder inD.citrireached 86.67% at 7 d post-treatment and 100% at 14 d post-treatment under field conditions. Our study revealed that strain ZJPL08 infectedD.citriby hyphae penetrating directly through the cuticle and into the body cavity and tissues. These findings show thatP. lilacinumstrain ZJPL08 has potential for the effective control ofD.citri.