ABSTRACT
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Seed-and soil-borne plant pathogens continue to be major constraints on
crop production worldwide. Until recently, their control has been largely
dependent on the use of synthetic chemicals such as fumigants and
fungicides, particularly where no good disease resistance is available
within plants. However, the use of the soil sterilant methyl bromide has been
banned, and the number of active ingredients available for use in chemical
fungicides is gradually decreasing due to concerns over environmental
impact and safety issues, including residues in food. The plant pathogens’
development of resistance to many fungicides is also a problem. Conse-
quently, there is considerable interest in the development of alternative plant
disease control methods. These may include traditional approaches such as
breeding, crop rotations, cultivation techniques, as well as additions of
organic matter, compost or other nutrients, which modify the environment
physically in the glasshouse or the field. However, perhaps the greatest
interest in the last few years has been in the development of biological
disease control, particularly as more commercial biocontrol products (bio-
logical pesticides or biopesticides) reach the market. Biological control
agents or biocontrol agents (BCAs) in this chapter are defined as those
microorganisms which can be used to eliminate or reduce pathogens or to
decrease damage caused by them. Similarly, plant growth-promoting
rhizobacteria (PGPR), also called biofertilizers, are being developed along
similar lines. Biofertilizers will be further discussed in Chapter 20. Both
types of organisms traditionally consist of preparations of microorganisms
selected from nature, which are grown under controlled conditions in a
fermentation process and formulated for application to plants, seeds or soil in
ways similar to those used for synthetic chemical pesticides.
