Beschreibung:
<p>The aim of this study was to evaluate the <em>in vitro</em> susceptibility of larvae unfed of  <em>Rhipicephalus microplus</em> to different isolates of entomopathogenic fungi native of soil of livestock units and know the characteristics of growth and inoculum potential of isolates that showed to be more pathogenic. Pathogenicity and virulence of isolates of <em>Metarhizium anisopliae</em> <em>sensu lato</em> (Ma), <em>Beauveria bassiana</em> (Bb) and, <em>Isaria fumorosea</em> (Ifr) was evaluated in <em>R. microplus</em> larvae of 7 days old, exposed by immersion in an aqueous solution at concentration of 1x10<sup>8</sup> conidia / ml. Ma135 and Ma133 isolates, showed high pathogenicity with 100 and 94% mortality, with LC<sub>50</sub> values ​​of 5.2x10<sup>4</sup> and 2.5x10<sup>4</sup> conidia / ml, respectively. In these isolates, the production of spores was 1.0x10¹º conidia / ml, and the radial mycelial growth were 3.07 and 3.60 mm / day, respectively. These results demonstrate that the isolated Ma135 and Ma133, can be considered as potential biocontrol agents in <em>R. microplus</em> larvae</p>