Biocontrol refers to the use of biological methods for controlling plant diseases and pests. It is a holistic approach that seeks to develop an understanding of the webs of interaction between the group of organisms that constitute the field fauna and flora, as opposed to the use of harmful chemicals as pesticides and weedicides. Such chemicals are not just a threat to both animals and human, but also contribute to pollution.
Dragonflies are natural predators which are effective against mosquitoes. They eat hundreds of mosquitoes each day. Thus, they are used to control the population of mosquitoes.
Ladybird is a beetle is useful in controlling aphids.