First Report of Aspergillus aculeatus Colonizing Protaetia brevitarsis Larvae: Pathogenicity and Dose-Dependent...

Widespread chemical pesticide use in agriculture threatens environmental and human health, creating urgent demand for sustainable alternatives like entomopathogenic fungi. However, effective entomopathogenic fungi for Protaetia brevitarsis remain scarce. This study first isolated and identified the Aspergillus aculeatus strain JBQM-1 from naturally infected P. brevitarsis larvae. Its identity was confirmed via morphological analysis, ITS rDNA sequencing, and calmodulin gene phylogeny. The calmodulin gene was used to address the limitation of ITS alone in distinguishing closely related Aspergillus species, ensuring accurate identification. JBQM-1 spores showed time-dependent germination in potato dextrose broth(PDB)medium, reaching 96.75% by 8 h. This rapid germination is key to timely host infection, supporting its biocontrol potential. Pathogenicity assays revealed JBQM-1's dose- and time-dependent virulence: 71% larval mortality at 1.0 × 10⁹ conidia per milliliter by day 7, with no mortality in the first 48 h. A heat-inactivated control assay was conducted to rule out non-infectious factors. The heat-inactivated group had 6.67 ± 3.34% mortality, which was not statistically different from the control group's 4.44 ± 1.92% mortality. No hyphal outgrowth was observed on dead larvae from the heat-inactivated group after 72 h incubation in moist chambers. This confirms JBQM-1's high virulence, expands A. aculeatus' host range, and highlights its potential as a biocontrol agent, providing new microbial resources for sustainable pest control.