Identification of a new Cordyceps javanica fungus isolate and its toxicity evaluation against Asian citrus psyllid

The Asian citrus psyllid, Diaphorina citri Kuwayama, is the most serious pest of citrus worldwide. It acts as a vector for a group of phloem-limited bacteria (Candidatus Liberibacter spp.) that causes Huanglongbing (HLB) disease. Thus, D. citri management is an important strategy against HLB, and biological control is currently considered as the most effective method because of the unsustainable and negative side effects of chemical control. Here, we isolated a new strain of entomopathogenic fungus, Cordyceps javanica (GZQ-1), from one cadaver of D. citri adult based on its morphological and phylogenetic data. Five conidial concentrations of the C. javanica pathogen (1 x 10(3), 1 x 10(4), 1 x 10(5), 1 x 10(6), and 1 x 10(7) conidia/ml) were assessed against six life stages of D. citri (1st-5th instar nymphs and adults). Results showed that C. javanica GZQ-1 was highly pathogenic to D. citri nymphs (69.49%-90.87% mortality) and adults (69.98% mortality). The LC50 and LT50 values of C. javanica against 1st-2nd instar (younger), 3rd-4th instar (middle aged), 5th instar (older), and adults were 1.20 x 10(5), 1.10 x 10(6), 4.47 x 10(6), 8.12 x 10(6) conidia/ml and 4.25, 4.51, 5.17, 5.49 days, respectively. Moreover, glasshouse experiments indicated that this C. javanica GZQ-1 caused higher infection rates of D. citri adults compared to two other fungal strains we previously isolated in the laboratory, Cordyceps fumosorosea (IF010) and Metarhizium anisopliae (CNGD7).