Ritesh Kumar
Senior Research Fellow (Plant Pathology)
ICAR Research Complex for Eastern Region-Research Centre
Senior Research Fellow (Plant Pathology)
ICAR Research Complex for Eastern Region-Research Centre
Ranchi-834010 Jharkhand, India
Email id.- ritesh.nstt@gmail.com
According
to Cook and Baker (1983) ‘Biological control is the reduction of the amount of
inoculum or disease producing activity of a pathogen accomplished by or through
one or more organisms other than man’. The terms “biological control” and its
abbreviated synonym “biocontrol” have been used in different fields of biology,
most notably entomology and plant pathology. In entomology, it has been used to
describe the use of live predatory insects, entomopathogenic nematodes, or microbial
pathogens to suppress populations of different pest insects. In plant
pathology, the term applies to the use of microbial antagonists to suppress
diseases as well as the use of host specific pathogens to control weed
populations (Pal et al.,
2006). In both fields, the organism that
suppresses the pest or pathogen is referred to as the biological control
agent (BCA). More broadly, the term biological control may also be applied
to the use of the natural products extracted or fermented from various sources.
These formulations may be very simple mixtures of natural ingredients with
specific activities or complex mixtures with multiple effects on the host as
well as the target pest or pathogen.
The
environmental pollution caused by excessive use and misuse of agrochemicals, as
well as fear-mongering by some opponents of pesticides, has led to considerable
changes in people’s attitudes towards the use of pesticides in agriculture. At the
same time there is a demand from society for healthy foods with less chemical
residues, and a great concern for preservation of the environment. Over the
past one hundred years, research has repeatedly demonstrated that
phylogenetically diverse microorganisms can act as natural antagonists of
various plant pathogens. The interactions between microorganisms and plant
hosts can be complex. Interactions that lead to biocontrol can include
antibiosis, competition, induction of host resistance, and predation. The most
common approach to biological control consists of selecting antagonistic
microorganisms, studying their modes of action and developing a biological
control product.
Mechanisms
of biological control
Biological
control may be accomplished through several approaches including mass
introduction of antagonists, plant breeding, and specific cultural practices
aimed at modifying the microbial balance.
Following
are the mechanism on which biocontrol agents work (which are never mutually
exclusive):
Antibiosis
Antibiosis
has been defined as the interactions that involve a low-molecular weight
compound or an antibiotic produced by a microorganism that has a direct effect
on another microorganism. The may be involved and play an important role in plant
disease suppression by certain bacteria and fungi.
Competition
This
process is considered to be an indirect interaction whereby pathogens are
excluded by depletion of a food base or by physical occupation of site. Biocontrol
by nutrient competition can occur when the biocontrol agent decreases the
availability of a particular substance thereby limiting the growth of the
pathogen. Particularly, the biocontrol agents have a more efficient uptake or
utilizing system for the substance than do the pathogens.
a biocontrol agent can provide plant protection by
efficient interception of these stimulating factors before pathogens can use
them.
Mycoparasitism
Mycoparasitism
is a process by which biocontrol fungi may attack pathogenic fungi. Fungi that
are parasitic on other fungi are usually referred to as mycoparasites. Many
mycoparasites occur on a wide range of fungi and some of them have been
proposed to play an important role in disease control.
Cell wall degrading enzymes
Extracellular
hydrolytic enzymes produced by microbes may also play a role in suppression of
plant pathogenic fungi. Chitin and b-1,3-glucans are major constituents of many
fungal cell walls. Several studies have demonstrated in vitro lysis of fungal
cell walls either by chitinase or b-1, 3-glucanase alone or in combination. Recently,
genetic evidence for the role of these enzymes in biocontrol has been obtained.
A chitinase (ChiA) deficient mutant of Serratia marcescens was shown to
have reduced inhibition of fungal germ tube elongation and reduced biocontrol
of Fusarium wilt of pea seedling in a greenhouse assay (Lam and
Gaffney, 1993).
Induced resistance
The
inducible resistance in plants to a variety of pathogens is known as systemic
acquired resistance (SAR) which may be induced by inoculating plants either
with a necrogenic pathogen or nonpathogen or with certain natural or synthetic
chemical compounds (Lam and Gaffney, 1993; Lo, 1998).
These defense responses may include the physical thickening of cell walls by lignifications,
deposition of callose, accumulation of antimicrobial low-molecular-weight
substances (e.g., phytoalexins), and synthesis of various proteins (e.g., chitinases,
glucanases, peroxidases, and other pathogenesisrelated (PR) proteins). This
defense system is also triggered when plants are colonized by plant growth-
promoting rhizobacteria (PGPR) and a few binucelate Rhizoctonia. Several strains of PGPR have been
shown to be effective in controlling plant diseases by inducing plant systemic
resistance.
Advantages of using biocontrol agents
- Safe to handle or use
- Occurs naturally
- High degree of host specificity
- Cost effective. Self perpetuation
- Eco Friendly
- Do not attack other species
Table
1. List of some biocontrol agents.
Sl.
No.
|
Biocontrol
Agents
|
Target
pathogen/pest/weed
|
|
1.
|
Fungal
|
Trichoderma spp.
|
Rhizoctonia,
Pythium, Fusarium and several soil and
foliar pathogen
|
Gliocladium
catenulatum
|
Pyhtium,
Phytophthora, Rhizoctonia, Botrytis.
|
||
Ampelomyces quisqualis
|
Powdery mildews
|
||
Gliocladium spp.
|
Several plant diseases
|
||
Coniothyrium minitans
|
Sclerotinia species
|
||
Cryptococcus albidus
|
Botrytis spp., Penicillium spp.
|
||
Verticillium lecanii
|
Whitefly, aphids and thrips
|
||
Metarhizium
anisopliae
|
black vine weevil, spittle bugs, cockroaches, termites
|
||
Beauveria
bassiana
|
whitefly, aphids, thrips, grasshoppers, locusts
|
||
Alternaria cassiae
|
Weedicide (Cassia
obtusifolia)
|
||
Cercospora rodmanii
|
Weedicide (Eichhornia
crassipes)
|
||
Colletotrichum coccodes
|
Weedicide, Velvetleaf (Abutilon theophrasti) in corn and soybeans
|
||
Colletotrichum
gloeosporioides f. sp cuscutae
|
Weedicide (Cuscuta chinensis, C. australis)
|
||
2.
|
Bacterial
|
Streptomyces
griseoviridis
|
Fusarium,
Pythium, Phytophthora.
|
Streptomyces
lydicus
|
powdery mildew
|
||
Bacillus
subtilis
|
powdery mildew, Botrytis, leaf spots
|
||
Bacillus
thuringiensis
|
caterpillars
|
Conclusion
and perspectives
A
successful biocontrol requires considerable understanding of cropping system;
disease epidemiology; the biology, ecology, and population dynamics of
biocontrol organisms; and the interactions among these variables (Lo, 1997). There
has been a significant increase in the number of biological disease control
agents registered or on the market worldwide in the last few years (Lo et al.,
1997). For example, there currently are approximately 30 bacterial and fungal
products for control of foliar, soil-borne and postharvest diseases. In recent
years, the progressive developments of biocontrol to plant diseases both in
research and application have been recognized in India. However, several
problems have been also created and various obstacles have stalled the
development of biocontrol, e.g. lack of constancy on its ffectiveness. Inconsistency
in effectiveness is a commonly encountered problem when biocontrol is employed
as a measure of plant disease control. Basic research is fully required before
integration between all abio- and/or biofactors which are beneficial to
increase efficacy of biocontrol.
Future prospects
There is
a growing demand for sound, bio-based pest management practices. An upswing in
commercial interests has also developed in the past few years. The future
success of the biological control industry will depend on innovative business
management, product marketing, extension education, and research. (Mathre et al., 1999). Increased demand for
organic produce and participation in home gardening activities by
pesticide-wary urban populations has enlarged the market for biocontrol
products. The field of plant pathology will contribute substantially to making
the 21st century the age of biotechnology by the development of innovative
biocontrol strategies.
References
Cook, R. and Baker, K. F. 1983. The Nature and
Practice of Biological Control of Plant Pathogens, American Phytopathological Society,
St Paul, Minnesota, 539.
Lam, S. T., and Gaffney, T. D. 1993. Biological
activities of bacteria used in plant pathogen control. Pages 291-320. in:
Biotechnology in Plant Disease Control. I. Chet, ed., John Wiley, New York .
Lo, C. T., Nelson, E. B., and Harman, G. E. 1997. Improved
biocontrol efficacy of Trichoderma harzianum 1295-22 for foliar phases
of turf diseases by use of spray application. Plant Dis. 81:1132 – 1138.
Lo, C.-T. 1998. General mechanisms of action of
microbial biocontrol agents. Plant Pathol. Bull. 7:155-166.
Lo, C-T. 1997. Biological control of turfgrass
diseases using Trichoderma harzianum. Plant Prot. Bull. 39: 207-225.
Mathre, D. E., Cook, R. J., and Callan N. W. 1999.
From discovery to use: Traversing the world of commercializing biocontrol
agents for plant disease control. Plant Dis. 83:972-983.
Pal, K. K. and B. McSpadden Gardener, 2006.
Biological Control of Plant Pathogens. The Plant Health Instructor DOI:
10.1094/PHI-A-2006-1117-02.
Note: This
article is only a compilation of the available information on the topic and the
source is cited/acknowledged in the text.
Yes, I agree with you that this is a problem in India still quite common. Therefore, the profession which is struggling with this problem is needed in any case. I remember when I needed their help on my plantation, I used this site https://youdo.com/india/ahmedabad-services/pest-control-services/ to find them. To do this, I needed just simply one o'clock of my time.
ReplyDelete