According and focus to the field observation on insect population around the word, I may notice that survival rate of insect from egg to adult is generally very low. The main factors for the high mortality is due to their natural enemies. Predators, parasitoids, and pathogens are natural enemies of insects. Some pathogens and parasitoids have sophisticated system for their survival and propagation, as which can avoid defense mechanism in the host and regulate their host development. Many interactions between natural enemies and host insects are, however, not yet known well, with the exception of some combinations. I am interested in the strategy of the natural enemies, how they adapt and regulate the hosts. I am especially focusing on insect viruses such as baculoviruses and entomopathogenic fungus such as Metarhizium, Beauveria from the point of view of physiology, ecology and evolution. My studies involve the impact of virus application against non-target organisms and the possibilities of developing resistance of insect pest against viral control agents. Besides, make the formula to do bioproduct to control insect pest Natural enemies of insect pests are used as biological control agents in the agriculture and forestry. My studies for insect viruses, fungi and its host are important because they contribute to improve practical uses of them as biological control agents.