Infection of the Stable Fly, Stomoxys calcitrans, L. 1758 (Diptera: Muscidae) by the Entomopathogenic Fungi Metarhizium anisopliae (Hypocreales: Clavicipitaceae) Negatively Affects Its Survival, Feeding Propensity, Fecundity, Fertility, and Fitness Parameters

Abstract

Entomopathogenic fungi can cause substantial mortality inharmful insects. Before killingthe insect, these pathogens start by negatively affecting the biological parameters of thehost. Prior to our study, the information about how fungal exposure affects the biologicalparameters of the stable fly,Stomoxys calcitranswas still elusive. Therefore, we aimed toassess the infection ofS. calcitranswith someMetarhizium anisopliaestrains, and theirimpact on feeding, fecundity, fertility and other life-history traits of this fly. Among the 11M. anisopliaestrains screened, we identified ICIPE 30 as the most virulentstrain againstS. calcitrans. We observed that the infectivity of this strain was sex and age-dependent.Infected maleS. calcitransdied earlier than their counterpart females. Older infectedS. calcitransdied faster than infected young ones. Also, male and femaleS. calcitranssuccessfully transmitted ICIPE 30 conidia to their mates. We demonstrated that infectionby ICIPE 30 extended the feeding time ofS. calcitransand consequently reduced thefeeding probability of the fly and the amount of blood taken. Using a dual test ovipositionbioassay, we determined that uninfected gravid femaleS. calcitransavoided laying eggson substrates amended with ICIPE 30 conidia. We showed that these conidia couldlower the hatchability of the eggs deposited by gravid females. Using, a no-choice test,we showed that gravid femaleS. calcitransinfected with ICIPE 30 laid fewer eggs thanuninfected females and those eggs hatched less. Using 11 strains ofM. anisopliaeandfour high concentrations of ICIPE 30 conidia, we verified thatS. calcitranslarvae were notsusceptible to fungal infection. Further, we showed that though these larvae were tolerantto fungal infection, there was a significant effect on their fitness, with contaminated larvaehaving a small bodyweight coupled with longer developmental time as compared touncontaminated larvae. Our study provides detailed information on how fungal infection Metarhizium anisopliaeAffectsStomoxys calcitransaffects the biology ofS. calcitransand the potential of usingM. anisopliaeICIPE 30 asa biopesticide to reduce the fly population. Such knowledge can assist in developingfungal-based control strategies against this harmful fly.