Determinação da CL90 e TL90 do isolado IBCB66 de Beauveria bassiana (Ascomycetes: Clavicipitaceae) para o controle de Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) Determination of LC 90 and LT 90 of IBCB66 Beauveria bassiana (Ascomycetes: Clavicipitaceae) isolate for Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) control

O presente trabalho teve por objetivo avaliar a patogenicidade e a virulência do isolado IBCB66 de Beauveria bassiana para larvas de Rhipicephalus (Boophilus) microplus. O isolado IBCB66 foi utilizado como padrão, com a finalidade de determinar a CL50 (Concentração Letal), CL90, TL50 (Tempo Letal) e TL90. O isolado IBCB66 foi testado em seis concentrações diferentes (5 × 10(6), 10(7), 5 × 10(7), 10(8), 5 × 10(8) e 10(9)) para determinar a porcentagem de mortalidade. A mortalidade total de larvas foi observada 18 dias após o início do teste no grupo tratado com 5 × 10(9) conídios.mL-1. A análise de Probit dos dados consignados apontou a CL50 e CL90 concentrações de 3 × 10(7) e 5 × 10(8) conídios.mL-1 e para TL50 e TL90, foram 10 e 16 dias, respectivamente.<br>The objective of this research was to evaluate the pathogenicity and the virulence of the IBCB66 isolate of Beauveria bassiana on infected larvae of Rhipicephalus (Boophilus) microplus. The IBCB66 fungus strain was used as standard isolates of B. bassiana against R. (B.) microplus larvae. The larval bioassay tests using the IBCB66 isolate were carried out to determine the (Lethal Concentration) LC50, LC90, (Lethal Time) LT50 and LT90. The IBCB66 fungus strain was tested at six different concentrations (5 × 10(6), 10(7), 5 × 10(7), 10(8), 5 × 10(8) and 10(9) conidia.mL-1) to determine the percentage of larval mortality. In addition, a Probit analysis was also performed. Total larval mortality was observed eighteen days after the beginning of the test in the group treated with 5 × 10(9) conidia.mL-1. The LC50 and LC90 were 3 × 10(7) and 5 × 10(8) respectively and the LT50 and LT90 were 10 and 16 days.