Virulence of Metarhizium anisopliae and Beauveria bassiana Against Common White Grubs in Nepal

Entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana were isolated from soils and white grubs cadavers from farmlands in Nepal. In the mortality studies, 8 isolates infected more than 80 % of the grubs, another 65 isolates infected more than 50 % of the grubs and the rest of the isolates had a low level of pathogenicity with 107 conidia/mL concentration. Five isolates were highly pathogenic against third instar larvae of Maladera affinis. The isolate, M. anisopliae M1 was the most virulent strain of all the evaluated isolates. LT50 of the tested isolates varied between 2-9 weeks. Isolates M1 and M6 had the highest mortality rates and required the shortest time to kill the white grub larvae. Assessment with fungus inocula with conidiospores and blastospores against three different instars of white grubs showed that a significantly larger numbers of second instar larvae were infected with the fungi than first and third instars. A comparison of indigenous and commercial isolates of M. anisopliae and B. bassiana with third instar larvae of Anomal