Effect of host plants on the virulence of nuclear polyhedrosis virus screened against Spodoptera litura (p.) (lepidoptera: Noctuidae)

Spodoptera litura is a very serious polyphagous pest on various economically important crops, which is controlled by nucleo polyhedro virus. Various bioassay methods were employed to test the virulence of S1NPV against S. litura reared on different host plants. In the first experiment, S. litura larvae were reared on different host plants such as Arachis hypogaea L., Brassica oleracea L., Gossypium hirsutum L., Rosa indica L. and Solanum tuberosum L. When they completed second instar, they were transferred to semi synthetic diet which was treated with different doses of S1NPV. The range of LT₅₀ values at different concentrations on different host plants was as follows: cabbage 4.877–7.382, cotton 5.623–8.606, groundnut 4.579–6.557, potato 5.455–7.806 and rose 5.800–9.032. In the second experiment, S. litura larvae were reared on semi-synthetic diet upto second instar and subsequently they were fed on leaf disc of different host plants, which were treated with S1NPV. The range of LT₅₀ values on different host plants was as follows: cabbage 4.933–7.954, cotton 6.135–9.394, groundnut 4.757–7.156, potato 5.584–9.164 and rose 6.312–9.816. In the third experiment, S. litura larvae were reared on different host plants till they complete second instar and they were screened against S1NPV in the laboratory on respective host plants by using leaf disc method. The range of LT₅₀ values on different host plants was as follows: cabbage 5.442–8.273, cotton 6.465–11.076, groundnut 5.167–7.867, potato 6.055–9.731 and rose 6.776–12.208. Among the different host plants, there was a significant difference in LT₅₀ between groundnut and cabbage. In all the experiments, the LT₅₀ values were highest in lower concentrations and vica versa.