Evaluating the virulence of Metarhizium anisopliae (Deuteromycotina: Hyphomycetes) and Beauveria bassiana (Ascomycota: Hypocreales) isolates to Arabian rhinoceros beetle, Oryctes agamemnon arabicus

Virulence of entomopathogenic fungi <em>Metarhizium anisopliae</em> and <em>Beauveria bassiana</em> were tested against Arabian Rhinoceros Beetle, <em>Oryctes agamemnon arabicus</em> larvae. Four concentrations (1×10⁵, 1×10⁷, 1×10⁹ and 1×10¹¹ conidia/mL^–1) of two locally isolated entomopathogenic fungi spore suspensions were used in this study via larval direct spraying. Results revealed that both isolates can cause high mortality rate reaching 100% after 29 days. However, <em>Beauveria bassiana</em> scored higher mortality rate in short time especially at the concentration of 1×10¹¹ conidia/ mL^–1 with lethal time (LT)₅₀ 12.75 and LT₉₀ 20.00; while, <em>Metarhizium anisopliae</em> caused the higher percentage of malformed adults. Moreover, both isolates affected insect’s life cycle particularly in the pupal stage which was reduced remarkably by almost 50% in comparison with the control treatment