NPV infected S. litura: A, typical NPV symptom of NPV ruptured infected larvae, usually die 4–9 days after infection, disintegrate and release a virus-laden fluid; B, slow move NPV infected swollen malformed pale brown larva; C, slow move NPV infected swollen malformed dark larva from 5th instar; D and E, malformed pre-pupae; F, laboratory propagative NPV infected larva; G, healthy larva.