Virulence of the Entomogenous Fungi Metarhizium anisopliae (Metschnikoff) Sorokin, M. flavoviride Gams and Rozsypal and Beauveria bassiana (Ballsamo) Vuillemin to Adoryphorus couloni (Burmeister) (Coleoptera: Scarabaeidae)

Two isolates of Metarhizium anisopliae and one isolate each of M. flavoviride and Beauveria bassiana, originally isolated from the redheaded pasture cockchafer, Adoryphorus couloni, were bioassayed for their virulence against both L3 larvae and adults. Only M. anisopliae DAT F‐001 was highly virulent to both larvae and adults. At a concentration of 2 × 106 spores/g sand‐peat, the LT50 for larvae at 20°C was 24.5 d. M. flavoviride was not pathogenic to larvae but was pathogenic to adults at all three concentrations tested (2 × 104 2 × 105, 2 × 106 spores/g sand‐peat mix). B. bassiana was not pathogenic to either larvae or adults, but this isolate, M. flavoviride and M. anisopliae DAT F‐001 reduced the number of eggs produced by 50‐75% at the 105 and 106 concentrations. Germination studies on the isolates showed that M. anisopliae DAT F‐001 and M. flavoviride could germinate at temperatures relevant to field conditions (5‐15 °C).