Abstract
The study was proposed to determine the susceptibility of the 1st and 3rd larval instars, and adults of the Rhinoceros beetle, Oryctes agamemnon arabicus (Coleoptera: Scarabaeidae) to infection and subsequent death by exposure to three commercial entomopathogenic fungi; (CFEF) products [Naturalis (Beauveria bassiana), Met52 (Metarhizium anisopliae) and PreFeRal (Isaria fumosorosea)] in the laboratory. Three concentrations of each CFEF were used for dose response mortality against both 1st and 3rd larval instars, whereas only 2 concentrations were used against the adult stage. Mortality rates of the 1st instar larvae reached up to 75.2, 69.1 and 46.6% at the concentrations (2.3 x 10(7) conidia / ml) of Naturalis (B. bassiana), (5.5 x 10(9) conidia / ml) of Met52 (M. anisopliae) and (2 x 10(9) CFU/g) of PreFeRal (I. fumosorosea), respectively. Similarly, at the same concentrations, the accumulated mortality of 3rd instar larvae recorded 59.1, 43.8 and 32.6% for Naturalis, Met 52 and PreFeRal, respectively. However, for O. agamemnon adults, correspondent mortality rates were lower than that of larval stage where reached 46.3, 37.6 and 27.2% for Naturalis, Met52 and PreFeRal, respectively. Mycosis test was carried out to confirm the entomopathogenic fungus infection in dead larvae and adults. Overall, mycosis percentages ranged 77-97, 85-96 and. 82-93% in 1st, 3rd instar larvae and adults of O. agamemnon, respectively. The LT50 values of the 3rd instar O. agamemnon larvae ranged 6.3-10.1, 5.4-8.05 and 5.9-9.2 days for the two concentrations that achieved 50% mortality for Naturalis, Met52 and PreFeRal, respectively. For adults, the correspondent LT50 values ranged 7.7-12.5, 7.0-10.5 and 6.9-11.2 days for same treated products, respectively. Generally, among the tested CFEF, Met52 showed the fastest effect in both larvae and adults, followed by PreFeRal and Naturalis. However, in terms of total mortality achieved, Naturalis was the most efficient one, followed by Met52 and then PreFeRal.