Virulence of Entomopathogenic Fungi in Nonfed Larvae and Engorged Females ofRhipicephalus sanguineusSensu Lato and Its Effect on Reproductive Potential

Abstract

Virulence of 10 isolates of entomopathogenic fungi native to Mexico and their effect on reproductive behavior were evaluated in nonfed larvae and engorged females of R. sanguineus sensu lato (Latreille). Virulence was evaluated by immersion in a concentration of 1 x 108 conidia per milliliter, while checks received the same aqueous formulation but without conidia. Reproductive potential was determined by calculating Reproductive Efficiency Index (eggs laid per engorged female weight) and Reproductive Aptitude Index (eggs hatched as larvae per engorged female weight). Results of bioassays on nonfed larvae showed that 40% of the isolates were able to kill ≥90% at 20 days post-treatment. Isolate Metarhizium anisopliae (Metchnikoff) Sorokin 135 with an LC50 of 1 x 106 killed 97%, while Beauveria bassiana (Bals.-Criv.) Vuill. Bb154 with an LC50 of 8 x 106 killed 90%. In engorged females, 70% of isolates killed ≥90% at 15 days post-treatment; isolate Bb154 reduced egg oviposition 83% and hatchability 96%. The isolates should be considered potential biological control agents for R. sanguineus.