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

Xiao‐Sheng Chen,Bao‐Li Qiu,Shaukat Ali,Chang‐Fei Guo,Da Ou,Li‐He Zhang

doi:10.1002/mbo3.760

Abstract

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 × 103, 1 × 104, 1 × 105, 1 × 106, and 1 × 107 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 × 105, 1.10 × 106, 4.47 × 106, 8.12 × 106 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).

Highlights

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is one of the most economically important pests of cit‐ rus worldwide
We isolated a new strain of entomopathogenic fun‐ gus, Cordyceps javanica (GZQ‐1), from one cadaver of D. citri adult based on its mor‐ phological and phylogenetic data
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)

Summary

| INTRODUCTION

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is one of the most economically important pests of cit‐ rus worldwide. In ad‐ dition to efficacy and cost, there are several advantages of using entomopathogenic fungi: they have broad‐spectrum insecticidal activity, diversified species range, complex metabolic types, and offer appropriate safety levels for humans and other non‐target organisms (Lacey, Frutos, Kaya, & Vail, 2001) They are easy to mass‐produce and development of host resistance against them is unlikely to occur. A new strain of entomopathogenic fun‐ gus, Cordyceps javanica (Friederichs & Bally), formerly Isaria javan‐ ica (Friederichs & Bally; Kepler et al, 2017), isolated from an adult cadaver of D. citri was identified through morphological as well as phylogenetic data The pathogenicity of this newly isolated strain to D. citri was analyzed through bioassays against different devel‐ opmental stages

| MATERIALS AND METHODS

Findings

| DISCUSSION