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

BACKGROUNDThe 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. METHODSAdult 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. RESULTSOur 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. CONCLUSIONOur 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.