Effect of Host Plants on the Infectivity and Yield of Nuclear Polyhedrosis Virus on Spodoptera litura (Fabricius)

Fourth instar larvae of Spodoptera litura (Fabricius) were reared on six species of virus treated host plants and a semi-synthetic diet and observed the influence of host plants on virus induced mortality, yield of nuclear polyhedrosis virus (NPV) and virulence of resultant virus. Larvae infected through tobacco leaves recorded the highest mortality (91.7%), while it was lowest through cotton leaves (61.7%). The pH of food materials had negative relationship (r = -0.85) with mortality. However, the variation among the host food with narrow range of pH (6.9 to 8) showed that the disparity of the influence of host food on the virus induced mortality may not be only due to pH. Larvae bred through virus contaminated semi-synthetic diet yielded maximum quantity of NPV (4.207x10⁹ POBs/g of larva) which was 1.95, 1.28, 1.25, 1.13, 1.11 and 1.08 folds greater than cotton, groundnut, sunflower, tobacco and castor, respectively. LC₅₀ and LT₅₀ of NPV were also influenced by host plants and semi-synthetic diet.