Acaricidal and pathogenic effects of the entomopathogenic fungus Beauveria bassiana on engorged females of the fowl tick, Argas persicus (Argasidae).

This study examined the acaricidal, histopathological and genotoxic effects of the entomopathogenic fungus Beauveria bassiana on engorged females of the fowl tick, Argas persicus. The acaricidal effect of B. bassiana (at 106-1010 conidia/mL) was concentration- and time-dependent. At 106 conidia/mL, the accumulated mortality of treated females ranged from 3.33 ± 3.3 to 13.33 ± 3.3% over 21 days. However, the mortality was remarkably increased after the application of 1010 conidia/mL, ranging from 6.67 ± 3.3 to 80 ± 5.8%. Females treated with various conidial concentrations exhibited complete inhibition of oviposition. Light and electron microscopic examination of the ovary of engorged female ticks at 3, 6 and 9 days after treatment with 107 conidia/mL revealed that the oocytes exhibited drastic changes that affected their growth and development. The overall damage observed in the ovary included loss of grape-like appearance, distortion of oocytes, cytoplasmic vacuolation, degeneration of organelles and myelin figure formation. Previtellogenic oocyte progression was completely inhibited as the vitellogenic phase was not observed. Random amplified polymorphic DNA (RAPD-PCR) and inter simple sequence repeat (ISSR) methods were used to assess the genotoxic effects of B. bassiana at 107 conidia/mL on engorged female A. persicus over 3 weeks. The lowest percentage of genomic template stability was recorded in paralyzed ticks after 3 weeks. The study demonstrated the efficacy of B. bassiana as a biocontrol agent against A. persicus as it interfered with its reproduction, movement and viability and disrupted its normal tissue and DNA integrity.