Exploration of indigenous strains of the green muscardine fungus from soils and their pathogenicity against the tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

In the recent years, the keen interest has been increased towards biological control-based management practices using entomopathogenic fungi (EPF) for the control of many economically important insects. In this management practices, selection of right strains of EPF is an important criteria to control the target pests in effective manner. In this context, this research work was formulated to find out environmentally effective strains of EPF in the soils of costal districts of Andhra Pradesh. Out of 135 soil samples collected, 8 soil samples yielded 8 strains of Metarhizium anisopliae. Among all 8 M. anisopliae isolates, the least median lethal concentration (LC 50 ) for 2nd instar of the tobacco caterpillar, Spodoptera litura (Lepidoptera: Noctuidae) was 1.24 × 10 5 spores ml -1 in M-7, followed by 1.72 × 10 5 spores ml -1 in M-5 and 1.86 × 10 5 spores ml -1 in M-4 in an increasing order. Likewise, the median lethal time (LT 50 ) values of different isolates of EPF against 2 nd instar of S.litura were calculated for a uniform highest dose of 1 × 10 8 spores ml −1 . Among all 8 M. anisopliae isolates, the lowest LT 50 was observed as 186.44 hours post infection (hpi) with M-5 and 189.34 hpi with M-7.