Effectiveness of Beauveria bassiana sensu lato strains for biological control against Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) in China.

Owing to the need to combat the spread of acaricide-resistant ticks, the development of long-term biological control has become a hot topic for tick control. In this study, we investigated the pathogenicity of three Beauveria bassiana isolates on the engorged female Rhipicephalus (Boophilus) microplus ticks using different conidial concentrations. The results showed that B. bassiana B.bAT17 was highly pathogenic against engorged R. (B.) microplus females, resulting in lethal time (LT50 and LT90) of 7.14 and 9.33 days at a concentration of 10(9)conidia/ml. R. (B.) microplus females treated with B. bassiana B.bAT17 significantly reduced the amount of ovipositioning; and most ticks died before they could begin to oviposit. Proteases and chitinases were analyzed in order to establish a screening method for identification of high virulent strains. This study has confirmed the significant pathogenic effect of entomopathogenic fungi against engorged R. (B.) microplus females in China, and further studies on the efficiency of the fungus against ticks in the field are required.