Why Biological Control?

The global sustainability agenda is increasing the demand for reduction in inputs into agricultural production while maintaining profitable yield of quality products. Plant diseases are a major constraint for both yield and product quality, but often tools for their control are ineffective or lacking. Biological control using antagonistic microorganisms has long been a subject of research resulting in a wide range of products that are now available and marketed in specific territories around the world. These preparations are often niche products with narrow uses. The research effort is intense both to develop new biological control agents (BCAs) and to obtain knowledge of the mechanisms underlying biological disease control. The prospects for biological control are promising. As a minimum, BCAs supplement other sustainable disease management practices such as disease resistance, and present opportunities for controlling diseases for which other approaches are ineffective or unavailable. We can realistically expect increasing use of BCAs to control crop diseases in ways that will benefit the environment.

The green agenda, specifically the need to focus on sustainable use of the resources available on our planet, is receiving increasing attention. The discipline of plant pathology can contribute to this agenda by improving agricultural efficiency, both in terms of increased yield and reduced environmental impact, in particular by reducing the estimated 20%–30% losses caused by pests and diseases (Oerke, 2006; Savary et al., 2019) and the side-effects of disease and pest control actions. Both can be achieved by reducing inputs per unit of production (e.g., watering, spraying pesticides and applying inorganic fertilizers) and reducing food and fodder spoilage after harvest. Disease resistance is also an important means of disease management but effective resistance is often not available, whether introduced by conventional means (plant breeding) or biotechnologically by genetic engineering including new genomic technologies.

Biological control is receiving increasing attention as an alternative means of disease control, both pre- and postharvest, especially where disease resistance or chemical control are not available...

BCAs identified so far include bacteria, fungi, oomycetes and viruses. Successful BCAs have been isolated from soil, especially disease-suppressive soils, as was the case for the parent strains of the BCA T22 mentioned above; they have also been isolated in association with plants, for example, the phyllosphere (above-ground plant surface) or rhizosphere (root surface), or from within plants, the endosphere (inside the plant). Many of the organisms identified occur naturally in several of these niches. In essence, there is a continuum from soil to rhizosphere to endosphere and phyllosphere.