Nucleopolyhedrovirus (NPV) is one of the most important pathogen of lepidopterans in nature.After getting infected, a "Wipfelkrankheit" (tree top disease) symptom could be easily identified, that is the infected larvae climb to the top of their host plants, get totally liquefied by the virus and died hanging with prolegs.Normally, healthy larvae prefer to hide in bark crevices or climb down the tree to the soil during daytime and climb back out on the leaves to feed at night.