Identification and biocontrol potential evaluation of a naturally occurring Metarhizium pingshaense isolate infecting tea weevil Myllocerinus aurolineatus Voss (Coleoptera: Curculionidae)

Background Tea weevil, Myllocerinus aurolineatus Voss (Coleoptera: Curculionidae), is an important insect pest in Chinese tea plantations. The primary method for controlling tea weevils involves the use chemical pesticides. Hence, there is an urgent need for environmentally friendly control strategies. To screen for potential pathogenic strains useful for the biocontrol of tea weevils, a naturally occurring Metarhizium pingshaense strain was isolated from a field-collected infected tea weevil larva for the first time in China. Results Morphological features and molecular characteristics revealed the isolate was an M. pingshaense strain, herein referred to as Ma0628. At 22 °C (tea weevil pupation temperature), the inoculation with M. pingshaense Ma0628 resulted in a corrected cumulative late instar larval mortality rate exceeding 76% at 11 days after the inoculation with the 1 × 10 8 conidia/ml spore suspension using the immersion or soil-mixing method. Accordingly, the median lethal concentrations were 4.49 × 10 3 and 3.76 × 10 2 conidia/ml for the immersion and soil-mixing inoculation methods, respectively. Furthermore, the corrected cumulative adult mortality rate reached 83.33% at 14 days after the inoculation with the 1 × 10 8 conidia/ml spore suspension. Conclusion The study results indicate that M. pingshaense strain Ma0628 is an entomopathogenic fungus pathogenic to tea weevil larvae and adults, suggesting it may be a potentially useful biocontrol agent for preventing M. aurolineatus infestations.