Natural enemies of insect pests play a key role in reducing the levels of pest populations below those causing economic injury. Both natural and applied biological control tactics can be important in successful management of pest populations. Biological control has the advantage of being self-perpetuating (once established), and it usually does not harm non-target organisms found in the environment. In addition, it is non-polluting or (as disruptive to the environment) as chemical pesticides, nor does it leave residues on food (a concern of many people today). However, the use of biological control does require detailed knowledge of the pest’s biology and the natural enemies associated with the pest and their impact.