Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
Evaluation of Risks Related to the Release of Biocontrol agents Active
against Plant Pathogens
J. Kumar
Department of Plant Pathology, G.B.P.U.A.& T., Pantnagar-263 145 (UK)
Biological control has been actively practiced for more than 100 years and the history of
biocontrol, its failures and successes, has been extensively reviewed by many researchers in
different parts of the world. Biological control is the deliberate use of one or more organisms to
suppress the growth or reduce the population of another organism to a level at which it is no
longer an economic problem. Two basic biological control methods include “classical” biological
control (CBC) and the “inundative” strategy. The classical strategy is also termed the “inoculative”
method, as it usually involves a small “dose” of an exotic biological control organism, applied once
or only occasionally, to a host population of weeds that is usually of foreign origin. The “inundative”
method involves single or multiple applications of a biological control agent to a pest at much
higher concentrations than ordinarily encountered. The term mycoherbicide usually refers to an
indigenous fungus applied in an inundative manner to control native weeds. The inundative
method involves application of sufficiently high levels of inoculum to the weed population, under
conditions that favour disease onset, to quickly create a disease epidemic among plants. The
organism that suppresses the pest or pathogen is known as Biological control agent (BCA). The
biocontrol agents provide protection against plant diseases either by direct action against the
pathogen (i.e. antagonism) and/or indirectly by reducing host susceptibility towards the pathogen.
As an antagonist, biocontrol agent may directly kill the pathogen by mycoparasitism and/or
antibiosis. It may adversely affect the growth and development of the pathogen either by antibiosis
or by competing for the nutrient, oxygen or space. Antagonist like Trichoderma is not only capable
of colonizing and killing the hyphae but also hard sclerotia of the fungal plant pathogens. Many
antibiotics have been isolated and characterized from fungal as well as bacterial biocontrol agents.
Soil pseudomonads generally produce fluorescent, yellow green, water-soluble siderophores with
both a hydroxamate and phenolate group. Biocontrol agents are microorganisms that adversely
affect the population of another microorganism (e.g. target pathogen) growing in association with
them. Generally biocontrol agents have potential to interfere in the life process of plant pathogens
both directly as well as indirectly. Biocontrol agents include virtually all classes of organisms’ e.g.
fungi, bacteria, nematodes, protozoa, viruses and seed plants.
Advantages and benefits of Biological control- various advantages of biocontrol are as follows.
• Reduce the use of chemical-based fungicides.
• Reduce the risk of developing pathogen resistant to traditional chemicals.
• Safer to use.
• More stable than chemical pesticides if stored properly.
• Lower re-entry interval (R.E.I.) times.
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