Age Related Response of Tobacco Caterpillar, Spodoptera litura (Fabricius) (Lepidoptera:Noctuidae) to Biovirus-S, a Commercial Formulation of Nuclear Polyhedrosis Virus

Laboratory tests were carried out to evaluate the effectiveness of Biovirus-S, a commercial formulation of nuclear polyhedrosis virus (Sl NPV) against the different age groups of Spodoptera litura (Fabricius) larvae. The susceptibility of the larvae correlated negatively with the larval period of development. LC₅₀ values of one day old larvae were found 2.7, 277.0 and 61951.2 times more susceptible than three, five and eight day old larvae, respectively. Ten-day-old larvae required comparatively higher concentrations of Biovirus-S (1.39x10¹⁰ POBs/ml), thereby indicating decreased susceptibility.