Which of the following is a common method of biological pest control?

Introducing natural predators into the environment is a well-established method of biological pest control. This approach leverages the natural relationships between various species to manage pest populations. By introducing or enhancing the presence of predators or parasites that specifically target pest species, it is possible to reduce pest populations without relying on chemical pesticides. This method promotes ecological balance and sustainability, as it often leads to a self-regulating system where the predator and pest populations maintain equilibrium.

In contrast, other methods mentioned involve different strategies. The application of synthetic pesticides focuses on chemical solutions to pest problems, which can lead to resistance in pest populations and negative effects on non-target organisms. Using genetically modified crops often aims to provide built-in resistance to pests but does not involve the direct ecological interactions that biological control entails. Planting cover crops can aid in managing weeds, but it does not specifically target pests in the same predatory manner as introducing natural enemies does.