Entomopathogenic potential of Metarhizium anisopliae isolated from engorged females and tested in eggs and larvae of Boophilus microplus (Acari: Ixodidae).

The purpose of this work was to evaluate the in vitro virulence of three isolates of Metarhizium anisopliae var. anisopliae to eggs and larvae of the tick Boophilus microplus. The fungus tested was isolated from engorged females of B. microplus collected in the field, and identified as Ma01, Ma02 e Ma04. These isolates were evaluated by immersion of eggs and larvae in suspension with different conidial concentrations: 10(5), 10(6), 10(7) e 10(8) conidia/ml. In each isolate there was a treatment group for each spore concentration and a control group with 10 repetitions. It was observed in the treated egg groups that there was a hatching percentage that was much less than that observed in the control groups. This was in inverse proportion to the conidia concentration/ml. Larval bioassays of all the tested isolates resulted in a high mortality of larvae in direct proportion to the spore concentration/ml, 10 days after the conidia suspensions were inoculated. To consolidate the infection, the fungus used in bioassays was re-isolated.