Isolation of indigenous strains of the white halo fungus as a biological control agent against 3rd instar larvae of tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae)

The farmer interest in biological control-based management practices using entomopathogenic fungi (EPF) for the control of many economically important insects has increased. In this process, selection of effective strains of EPF is an important criterion to control the target insect pests in efficient 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, India. Out of 135 soil samples collected, 9 yielded 9 strains of Lecanicillium lecanii . Among all 9 L . lecanii isolates, the least median lethal concentration (LC 50 ) for 3rd instar larvae of the tobacco caterpillar, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), was 1.17 × 10 6 spores ml −1 in L-8, followed by 1.27 × 10 6 spores ml −1 in L-5 in an increasing order. Likewise, the median lethal time (LT 50 ) values of different isolates of EPF against the 3rd instar of S . litura were calculated for the uniform highest concentration of 1 × 10 8 spores ml −1 . Among all 9 L . lecanii isolates, the lowest median lethal time (LT 50 ) was observed as 7.70 days by L-8, followed by 7.77 days by L-5 and 8.50 days by L-7.