<i>Beauveria caledonica</i>: identification, microsclerotia production, and biocontrol activity against lepidopteran pests

<p dir="ltr"><i>Beauveria</i> is a fungal genus with notable biocontrol activity against pests and diseases, as well as the ability to produce bioactive metabolites. While conidia are commonly used as the active ingredient in biopesticides, their field performance is limited by abiotic stress and labour-intensive solid-state fermentation (SSF) production. This has driven interest in alternative fungal propagules such as microsclerotia (MS), which are more stress-tolerant and can germinate to produce infective conidia. In this study, we identified and characterised an entomopathogenic fungus isolated from a cadaver of <i>Hylurgus ligniperda</i> (<i>Coleoptera: Scolytidae</i>) in New Zealand, evaluated its biological activity against two lepidopteran pests, and established liquid fermentation conditions for MS production. The fungus was identified as Beauveria caledonica based on ITS, EF1-a and B-tubulin gene sequences. Among four culture media, only the one with a C/N ratio of 50:1 supported MS formation, with aggregates appearing after 8 days and MS after 10 days. The maximum yield reached 47 MS/mL and 12.13 g/L biomass. MS exhibited 100% myceliogenic germination and produced 6.4 x 10⁵ conidia per MS. Virulence assays showed that conidia at 1 x 10⁷ conidia/mL caused 55% mortality in <i>Plutella xylostella</i> larvae and 40% in <i>Spodoptera frugiperda</i> larvae, indicating moderate virulence against these two species. To the best of our knowledge this is the first report of MS formation by <i>B. caledonica</i>. Further optimisation of fermentation conditions and host range studies are needed to fully realise the potential of <i>B. caledonica</i> microsclerotia as a robust and versatile biocontrol agent for sustainable pest management.</p>