Sex-specific sub-lethal effects of low virulence entomopathogenic fungi may boost the Sterile Insect Technique

Abstract

BACKGROUND: The Sterile Insect Technique (SIT) is a species-specific method for controlling insect pests. Recent studies have explored the combination of SIT with entomopathogenic microorganisms, known as boosted-SIT, to enhance its effectiveness. This study aimed to evaluate the potential of the entomopathogenic fungi, Metarhizium anisopliae, in boosting the SIT for managing the oriental fruit fly, Bactrocera dorsalis. METHODS: Adult flies from a laboratory population of B. dorsalis were inoculated with one of eight strains of M. anisopliae to assess fungus virulence in each sex. Ideally, boosted-SIT should minimally impact sterile males and reduce female fecundity maximally. A brief exposure to fungal spores was efficient to infect males, and for them to transmit the fungus to females when hosted together for 24 hours. RESULTS: Our results showed significant variations in the mortality induced by the strains in males, but not in females that exhibited low mortality. Strains varied in their sub-lethal effects on female fecundity, with almost a two-fold variation among strains. Furthermore, strains that had the lowest virulence on males tended to reduce female fecundity the most. CONCLUSION: Our study brings a proof of concept that it is possible to leverage boosted-SIT using carefully selected pathogen strains and their sub-lethal effects on both the male and female fruit fly.