Susceptibility of tobacco caterpillar, Spodoptera litura Fab. (Noctuidae: Lepidoptera) to certain entomogenous fungi.

Five isolates of three entomogenous fungi were bioassayed for their infectivity to second instar larvae of Spodoptera litura Fab. by spraying the host larvae with the conidial suspension in the laboratory. Of them, Beauveria bassiana (Bals.) Vuill. (Bapatla isolate) was found to be the most virulent recording the lowest LC 50 of 19.90 × 10 5 conidia ml -1 . Tbe LC 50 values of the Bangalore and New Delhi isolates of B. bassiana, Paecilomyces fumosoroseus (Wize) Brown and Smith and P. farinosus (Holm ex Gray) Brown and Smith ranged from 5.55 × l0 8 to 5.58 × 10 9 conidia ml -1 , Bioassay of second, third and fourth instar larvae of S. litura for their susceptibility to Bapatla isolate or B. bassiana showed that susceptibility decreased with increase in age of the larvae in terms of both LC 50 and LT 50 .