Phylogenetic relationships and effectiveness of four Beauveria bassiana sensu lato strains for control of Haemaphysalis longicornis (Acari: Ixodidae)

Abstract

Haemaphysalis longicornis (Acari: Ixodidae) is an important vector tick that is widely distributed around the world. In many regions, this tick acts as vector of a wide range of pathogens to humans and animals, and its control is mainly based on the use of chemical pesticides. However, the occurrence of some adverse effects, such as tick resistance to pesticides and food and environmental contamination, are driving the need to develop more effective and environmentally sound approaches to control and prevent ticks. As an alternative control strategy, entomopathogenic fungi have been extensively used for the control of pests and cause high mortality in various ticks. In this study, we identified four isolates of Beauveria bassiana sensu lato from insects and investigated their pathogenicity against different developmental stages of H. longicornis (eggs, unfed larvae, unfed nymphs and engorged females). Phylogenetic analysis demonstrated that the four isolates of B. bassiana clustered into two clades. Four isolates showed different acaricidal qualities: the isolate from Cerambycidae (EF3) exhibited the highest pathogenicity to all developmental tick stages tested. High doses (1 × 107 conidia/ml) of the clade I fungi collected from Cryptotympana atrata fabricus (Cicadidae) (EF1), Cimicidae (EF2), and Boettcherisca peregrine (Sarcophagidae) (EF4) also showed virulence against H. longicornis, with high doses of the fungi application causing higher mortality than control group. Altogether, this study demonstrated that all four isolates of B. bassiana showed high virulence toward different developmental stages of H. longicornis, and therefore, they can be of potential use as biological control agents of ticks.