Biological control is a method of restricting the effects of harmful animals, pathogens, and plants using other useful organisms and changing this technique with 
biological pest control methods. There are many pest control methods available to choose from, but they can be loosely grouped into three categories: classical techniques, augmentative techniques, and conservationist techniques. In each of these three techniques, a species or a group of species is deliberately released in a cropland area to serve as predators of another species, which is acting as a plague. The real variations come from the details. For full article go to 