Efficacy of a native isolate of the entomopathogenic fungus Metarhizium anisopliae against larval tick outbreaks under semifield conditions

This study aimed to evaluate Metarhizium anisopliae (Metschn.) Sorokin (Hypocreales: Clavicipitaceae) persistence in the soil and its impact on Rhipicephalus microplus Canestrini (Acari: Ixodidae) larval recovery in a semifield trial after the treatment of female ticks. Nine strains from the genus Metarhizium Sorokin were isolated from the soil in Brazil and taxonomically classified using the ef1-α gene. The thermotolerance of the strains and their in vitro virulence to tick larvae were tested. One M. anisopliae strain was selected and formulated for the semifield test. The presence of M. anisopliae in the soil ranged from 0.4 × 105 to 1.4 × 105 colony forming units per gram of soil after the treatment during the five months of the survey. The fungus-treated grass pots had significantly fewer larvae than did the control pots. Evidence was gathered about the soil persistence of a native M. anisopliae strain and its efficacy in the biological control of ticks.