Resumo

OLIVEIRA, Renato C. de; NEVES, Pedro M.O.J.  e  ALVES, Luís F.A.. Entomopathogenic fungi selection to control Oligonychus yothersi (McGregor) (Acari: Tetranychidae) in Paraguay tea crops (Ilex paraguariensis St. Hill.). Neotrop. Entomol. [online]. 2004, vol.33, n.3, pp. 347-351. ISSN 1519-566X.  http://dx.doi.org/10.1590/S1519-566X2004000300012.

The virulence of strains of the entomopathogenic fungi Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus was evaluated on Oligonychus yothersi (McGregor) in laboratory. The bioassays for strain selection and determination of LD₅₀ and LT₅₀ were elaborated with leaf disks of Paraguay tea infested with 10 adult females of the mite. Groups of five disks were sprayed with 1 ml of the suspension standardized in 1.0x10⁷ conidia per ml (50 mites per treatment) of each strain. After that, the disks were maintained floating in distilled water in plastic boxes (3 cm diameter and 1.5 cm height), in environmental chamber (temperature: 25 ± 1ºC; RH: 71 ± 10% and 12h photophase). Five days after the inoculation the total mortality was evaluated, and the dead mites were transferred to humid chamber. Six days after death, the sporulation in the cadavers was examined under an optical microscope. B. bassiana presented great potential as a microbial control agent, and can be incorporated in integrated pest management of the Paraguay tea red mite, O. yothersi. The B. bassiana strains UEL02, UEL08, UEL10, UEL50, CG082, CG166, CG375, CG424 and CG481, were the most virulent, with corrected and confirmed mortality higher than 70% and estimated value of CL₅₀ varying between 1.9x10⁶ and 6.0x10⁷ conidia per ml and TL₅₀ varying between 3.3 and 4.3 days.

Palavras-chave : Red mite; bioacaricide; patogenicity; virulence.