Biological Control by Microorganisms


Biological control is the use of natural enemies to reduce the numbers of a damaging organism, which can be anything from a bacterium to a rabbit. Such natural enemies include pathogenic and competitor microorganisms. Biological control agents can be both less toxic and more flexible than chemical pesticides, although given the complexities of biological systems a relatively high level of understanding of the target organism is required. Although they may be more sympathetically regulated, their high specificity can impose limitations on commercial development. Biological control includes a wide range of approaches, from natural predators to biologically produced molecules. The focus of this article is on microorganisms, including viruses, bacteria, fungi and protozoans. Though many of these cause disease in or poison their target through toxin production, others may act by a different route, for example, by outcompeting the target organism or by excluding it from an ecological niche.

Key Concepts:

  • Biological control is use of material of biological origin to control the numbers or effects of a target organism.

  • Biological control includes the use of predators, competitors, pathogens and compounds of biological origin.

  • Microorganisms used include viruses, bacteria, fungi and protozoans. These may cause disease, or may compete with or otherwise limit the target organism.

  • Biological controls tend to be highly specific. Although this generally makes them environmentally benign, it also means that they need to be used in a highly informed way.

  • Both specificity and the cost and nature of the agents used have limited the use of biological control. All approaches combined account for only approximately 5% of the global pesticides market, although this figure is rising.

Keywords: biological control; biopesticides; microorganisms; bacteria; fungi; viruses; bacteriophages; protozoans

Figure 1.

Biological control of spider mites. Comparison between chemical and biological control of the spider mite Tetranychus urticae in a commercial cucumber crop in Finland. D, treatment with the acaricide dicofol. The predatory mite was Phytoseiulus persimilis. Economic threshold level of spider mite is 20 mites per 5 cm2. The predatory mite was introduced in the middle of February, and provided a season‐long, effective control of the pest. Reproduced with permission from Markkula et al..

Figure 2.

The global pesticides market, 2008–2014. Data from BCC Research .

Figure 3.

Insecticidal effect of B. thuringiensis (Bt). These effects are produced by a complex of crystalline toxins. Eaten by the insect larvae these damage the gut, allowing a lethal generalised infection. The infection generally does not spread to new hosts.

Figure 4.

Baculovirus structure. Baculoviruses all form protective occlusion bodies, or ‘OBs’ around the infectious nucleocapsids, and are divided into two genera. These are the Nucleopolyhedroviruses, in which a single OB contains multiple infectious units and the Granuloviruses, in which each OB contains a single infectious unit. During infection of the host, a nonoccluded or ‘budded’ form of the virus is produced, which lacks the occlusion body. The agents formerly classified as ‘nonoccluding baculoviruses’, including O. rhinoceros virus, are now considered to belong to an unclassified group of baculovirus‐like agents.

Figure 5.

Insecticidal effect of generalised baculovirus infection. Baculoviruses within OBs are eaten by insect larvae. The OB dissolves in the insect gut releasing viruses that infect the cells of the gut by growing there. The virus then spreads throughout the body of the insect, killing it and releasing large amounts of virus from the liquefied mass that results.

Figure 6.

A bacterial virus (bacteriophage) of the family Myoviridae, showing the contractile tail structure. © AmpliPhi Biosciences.



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Further Reading

BCC Research (2012) Biopesticides: The Global Market; Report CHM029D. Wellesley, MA, USA: BCC Research LLC.

Copping LG (2001) The Biopesticide Manual: A World Compendium of Naturally Occurring Biopesticides. Bracknell: BCPC Publications.

Hall FR and Menn JJ (eds) (1998) Biopesticides: Use and Delivery. Totowa, NJ: Humana Press.

Harper DR, Anderson J and Enright MC (2011) Phage Therapy: Delivering on the Promise. Therapeutic Delivery 2: 935–947.

Web Links

Crickmore N, Baum J, Bravo A et al. (2013) ‘Bacillus thuringiensis toxin nomenclature’.

Environmental Protection Agency (EPA) (2013) Biopesticides.

ProMED (2000) ProMed‐mail. International Society for Infectious Diseases.

Shelton A (2013) Biological Control: A Guide to Natural Enemies in North America. Ithaca, New York: Cornell University.

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How to Cite close
Harper, David R(Jun 2013) Biological Control by Microorganisms. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000344.pub3]