The production of the nucleopolyhedrovirus (NPV) of the tobacco cutworm, Spodoptera litura was studied to determine the optimum conditions for in vivo production using homologous host larvae reared on artificial diet. We compared NPV production in 7, 8, 9 and 10-day-old larvae and found that 9-day-old larvae gave the highest virus yield. The optimum dose was determined by infecting 9-day old larvae (weighing 125–155 mg) with a range of doses. The maximum NPV production achieved was 3.91 × 109 polyhedral inclusion bodies (PIBs) per larva using an inoculum of 4.8 × 106 PIBs. A 7-day incubation period was found to be optimum for NPV production. Moribund larvae were found to be more suitable for handling and for the mass production of virus than dead ones.

The effects of neem seed kernel extract (NSKE), neem oil (NO) and nucleopolyhedrovirus (NPV) of the Spodoptera litura Fabricius (Lepidoptera: Noctuidae) on the mortality, feeding and development of S. litura were evaluated in the laboratory. Dose-dependent mortality was evident after NPV treatment, which also depended on larval age at treatment. Upon combining NPV with neem products, the percentage mortality was enhanced threefold even at reduced concentrations. The NSKE and NO significantly inhibited the growth and development of S. litura, and extended the duration of its larval and pupal stages. Oviposition period, adult longevity and fecundity were significantly reduced following treatment with neem products and with neem + NPV treatment. The efficiencies of conversion of ingested food (ECI) and digested food (ECD) were also significantly decreased by treatment with NSKE, NO and NPV, either alone or in combination.