ABSTRACT
Forty-five isolates of Aschersonia aleyrodis (1), Beauveria bassiana (32), Metarhizium anisopliae (10), Hirsutella sp.(1) and Paecilomyces farinosus (1) were evaluated for pathogenicity against the mite Tetranychus urticae. The mites were inoculated with suspensions containing 1.7 x 107 (Hirsutella sp.) or 5 x1 07 conidia/mL (other fungi) and maintained at 25 ± 1° C, 98% RH and 12 h photofase. A. aleyrodis and P. farinosus had low pathogenicity, causing less than 3% Abbott-corrected mortality five days after inoculation. All isolates of B. bassiana, M. anisopliae and Hirsutella sp. were pathogenic to T. urticae with mortalities increasing after the third day and peaking on the fourth or fifth day post inoculation. For B. bassiana, 19 isolates (59%) caused corrected mortalities between 60 to 80% after 5 days, and only 8 isolates (25%) caused corrected mortalities > 80%. For M. anisopliae, 8 isolates (80%) caused > 80% corrected mortality after 5 days, and 4 caused > 90% mortality. Hirsutella sp. caused 73% mortality 5 days after inoculation with 1.7 x 107 conidia/mL. Calcium oxalate crystals were observed inside 80 to 100% of mites infected with B. bassiana or M. anisopliae.
KEY WORDS:
Aschersonia aleyrodis; Beauveria bassiana; Metarhizium anisopliae; Hirsutella; Paecilomyces farinosus; Tetranychus urticae.