How can biological control organisms reduce plant disease?

Biological control of plant diseases utilizes organisms, known as antagonists, to reduce or prevent pathogen infection. These antagonists may occur naturally or be purposefully applied to a host plant.1

Antagonists reduce disease through several mechanisms:

• Antibiosis: Some antagonists produce antibiotics or toxic chemicals that inhibit or kill pathogens in close proximity.1
• Parasitism: Certain organisms act as parasites directly on the pathogens.1
• Competition: Antagonists may compete with pathogens for essential resources, such as food or nitrogen, thereby limiting the pathogen's population growth.1

Cultural practices can also support these natural defenses. For example, incorporating green manure into soil encourages saprotrophic microorganisms to consume available nutrients, depriving pathogens of the resources needed to thrive. Similarly, suppressive soils naturally harbor antagonists that limit pathogen damage.1

While biological control is an environmentally sound strategy, it requires careful consideration to avoid the unintended introduction of invasive species, which can disrupt local ecosystems.2