Which method involves the intentional addition of natural enemies to control pest populations?

The method involving the intentional addition of natural enemies to control pest populations is bioagent introduction. This approach leverages natural predators, parasites, or pathogens to reduce pest populations by targeting specific pests without harming non-target species significantly. By introducing these bioagents, the balance of the ecosystem can be restored, allowing natural control processes to take place.

Fertilization, while essential for plant growth, does not directly influence pest populations in the way that bioagent introduction does. Pesticide application typically refers to chemical treatments designed to eliminate pests rather than introducing biological controls. Physical removal involves manually eliminating pests, which can be labor-intensive and may not provide long-term solutions on its own.

Thus, bioagent introduction is a sustainable and environmentally friendly strategy that promotes ecological balance by harnessing naturally occurring organisms to manage pest populations effectively.