Phenotypic search for promising entomopathogenic fungal isolates to control pollen beetles

Abstract: Twenty five isolates of entomopathogenic fungi belonging to the species Beauveria bassiana (Balsamo) Vuillemin (21), B. brongniartii (Saccardo) Petch (2), Paecilomyces fumosoroseus (Wize) (1) and Metarhizium anisopliae Sorokin (1) were screened for virulence against pollen beetle Meligethes aeneus. Several of the selected B. bassiana isolates originated from naturally infected pollen beetles collected in Switzerland. For the laboratory bioassays adult pollen beetles were dipped into a conidial suspension of 1 x 107 spores per ml (0,05% Tween 80) and incubated at 22 °C, 70% rh, L:D 16:8. Infection rates were recorded after 15 days. Seven isolates of B. bassiana as well as the P. fumosoroseus isolate achieved infection rates of ≥ 67%. Twelve isolates caused intermediate infection rates of 34-66%, whereas five B. bassiana isolates showed infection rates of less than 33%.