Abstract
Susceptibility of the third larval instar of the rhinoceros beetle, Oryctes agamemnon (Burmeister) (Coleoptera: Scarabaeidae), to the infection with three native entomopathogenic fungi (EPFs), Beauveria bassiana, Metarhizium anisopliae, and Lecanicillium lecanii, was determined under laboratory conditions. Three concentrations (10(4), 10(6), and 10(8) conidia/ml) of each EPF isolate were tested. Respective mortality rates of the larvae reached 34.2, 48.1, and 55.5% for B. bassiana, 39.5, 57.4, and 60.8% for M. anisopliae, and 17.4, 26.4, and 29.2% for L. lecanii. Mycosis test was performed to confirm the fungal infection of dead larvae. The LT50 values for O. agamemnon larvae were 9.9 and 11.3days, for the concentration which achieved 50% mortality for B. bassiana and M. anisopliae, respectively. The proteolytic activity of the three EPFs was investigated under different factors (incubation periods, temperature, and pH of fungal cultures). The results showed that the maximum activity of protease, produced by the three EPFs, was recorded after 6days of incubation periods at 28 degrees C, in a medium initially adjusted to pH6.