What tool is commonly used in biological control?

Biological control is a pest management strategy that utilizes natural predators, parasites, or pathogens to regulate pest populations. Insects play a crucial role in this method; they can serve as biological control agents by preying on or parasitizing harmful pests. For instance, ladybugs are known to consume large quantities of aphids, while parasitic wasps can lay their eggs in or on pest insects, ultimately controlling their populations.

The other options do not align with the principles of biological control. Herbicides are chemical substances used to kill unwanted plants, not pests. Mechanical machinery refers to equipment used for physical pest removal or management, which does not involve biological organisms. Fertilizers are nutrients added to soil to support plant growth and do not have a role in pest control. Therefore, utilizing insects as natural enemies directly applies to the concept of biological control.