[In vitro patogenicity of the fungi Metarhizium anisopliae (Metschnikoff, 1879) Sorokin, 1883, on the tick Boophilus microplus (Canestrini,1887)].

The cattle tick Boophilus microplus is a serious concern to the Brazilian cattle industry. It causes decreased meat and milk production, low alimentary conversion, damage to leather and transmission of pathogens. The use of entomopathogenic fungi as biological control agents for ticks has shown promising results. This study tests the in vitro effects of two Metarhizium anisopliae isolates (E9 and 319) towards three stages of B. microplus: eggs, larvae and engorged females. The bioassays were composed of five treatment groups (concentrations: 10(5), 10(6), 10(7), 10(8) conidia/ml and the control) each one with ten repetitions. The stages were treated by immersion for three minutes. After the treatments, the females, eggs and larvae were incubated at 27 degrees C +/- 1 and RH >or= 80%. The main studied parameters were: percentage of larvae eclosion, percentage of larvae mortality and the indexes of nutritional and reproductive efficiency. In vitro tests of the fungal isolates showed effective control of the three stages of B. microplus, suggesting high potential for their use as a microbial control agent of the B. microplus tick.