Potential of entomopathogenic fungi for <i>Glossina austeni</i> control: insights into microbiome alterations and implications on sustainable management of the pest

Glossina austeni Newstead (Diptera: Glossinidae) is a competent vector of the trypanosomes causing human African trypanosomiasis and the African animal trypanosomosis. Management of this pest has primarily involved trapping methods, Sterile Insect Technique, and research into vector competence-symbiotic interactions. Nevertheless, the use of entomopathogenic fungi (EPF) in integrated pest management programs for G. austeni control remains limited. Moreover, different tsetse fly species exhibit varying susceptibility to different EPF strains, indicating that no single strain is universally effective. Therefore, our study aimed to identify candidate EPF isolates for G. austeni management, evaluate the effects of temperature on the radial growth of these potent isolates, and assess the impact of the candidate EPF on the gut microbiome of G. austeni. Consequently, 16 Metarhizium anisopliae (Metschn.) Sorokin isolates were screened against G. austeni using dry conidia in an infection chamber, with the most virulent isolates having LT₅₀ values of 3.95-9.37 d. Temperature significantly influenced the radial growth, conidia germination, and yield of these strains. There were also significant differences in conidia acquisition, retention and transmission between male and female G. austeni flies. Furthermore, all conidia receivers carried sufficient conidia, 5 d post-interaction with EPF-challenged conidia donors. Microbiome analysis revealed Wigglesworthia, Serratia, Klebsiella, and Escherichia as the most abundant taxa. Among the M. anisopliae isolates, ICIPE 82 exhibited the fastest radial growth and highest thermostability, hence selected as a potential biopesticide candidate for managing G. austeni. This study demonstrates the efficacy and potential of M. anisopliae ICIPE 82 as a biopesticide for controlling G. austeni.