This document discusses plant disease outbreaks and epidemics. It defines an outbreak as a sudden increase in disease occurrences in a particular place and time, while an epidemic is a change in disease over time and space that can affect regions or countries. Epidemics develop from a combination of susceptible hosts, virulent pathogens, and favorable environmental conditions over a long period. Factors like host genetics, crop type, and moisture levels can influence epidemic development. The document also outlines management strategies like computer modeling, forecasting, and warning systems to help control epidemics.

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2. DISEASE OUTBREAK AS
DISASTER IN AGRICULTURE
SUBMITTED TO
Dept of Agronomy
UAS,GKVK,BENGALURU
SUBMITTED BY
UPASANA MOHAPATRA
PALB 6290
PLANT BIOTECHNOLOGY
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3. Flow of Presentation
Conclusions
References
List of plant epidemic diseases
Management of epidemic diseases
Factors of epidemic
Disease outbreak and epidemic
Causes of epidemic
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4. DISEASE OUTBREAK
• In epidemiology, an outbreak is a sudden
increase in occurrences of a disease in a
particular time and place. It may affect a small
and localized group or impact upon thousands
of people crops across an entire continent.
• Outbreaks include epidemics, which is change
in plant disease in time and space..
• They may affect a region in a country or a
group of countries
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5. CAUSES OF EPIDEMIC
Plant disease epidemics develop as a result of the
timely combination of
• The same elements that result in plant disease
• Susceptible host plants
• A virulent pathogen
• Favourable environmental conditions over a relatively
long period of time.
• Humans may unwittingly help initiate and develop
epidemics through some of their activities,
e.g., by topping or pruning plants in wet weather.
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6. Schematic diagram of the interrelationships of the factors involved in plant
disease epidemics
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7. HOST FACTORS THAT AFFECT
THE DEVELOPMENT OF EPIDEMICS
• Levels of Genetic Resistance or Susceptibility
of the Host.
• Degree of Genetic Uniformity of Host Plants
• Type of Crop
• Age of Host Plants
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8. Levels of Genetic Resistance or Susceptibility
of the Host.
• Host plants carrying race-specific
(vertical)resistance do not allow a pathogen to
become established in them, and thus no
epidemic can develop.
• Host plants carrying partial
(horizontal)resistance will probably become
infected, but the rate at which the disease and
the epidemic will develop depends on the level
of resistance and the environmental conditions
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9. Degree of Genetic Uniformity
• The highest rates of epidemic development
generally occur in vegetatively propagated
crops,
• Intermediate rates in self-pollinatedcrops
• The lowest rates in cross-pollinated crops.
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10. Type of Crop
• In diseases of annual crops, such as corn, vegetables,
rice, and cotton, and in foliar, blossom, or fruit diseases
of trees and vines, epidemics generally develop much
more rapidly (usually in a few weeks) than they do in
diseases of branches and stems of perennial woody crops
such as fruit and forest trees.
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11. PATHOGEN FACTORS THAT AFFECT
DEVELOPMENT OF EPIDEMICS
1. Levels of Virulence
2. Quantity of Inoculum near Hosts
3. Type of Reproduction of the Pathogen
4. Ecology of the Pathogen
5. Mode of Spread of the Pathogen
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12. ENVIRONMENTAL FACTORS THAT AFFECT
DEVELOPMENT OF EPIDEMICS
• Moisture
• abundant, prolonged, or repeated high moisture,
whether in the form of rain, dew,or high humidity,
is the dominant factor in the development of most
epidemics of diseases
• Temperature
• Epidemics are sometimes favored by temperatures
higher or lower than the optimum for the plant
because they reduce the plant’s level of partial
resistance
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13. Schematic representation of epidemic caused in a crop in a field by a soil pathogen
over a 4-year period.
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14. (A) Lettuce heads infected by soilborne sclerotia of Sclerotinia sclerotiorum.
(B) Large field of lettuce heads killed by infections with airborne ascospores of
the same fungus.
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15. EFFECT OF HUMAN CULTURAL
PRACTICES
Site Selection and
Preparation
• Low-lying and poorly
drained and aerated
fields, especially if
near other infected
fields, tend to favor
theepidemics
Selection of
Propagative Material
• The use of seed,
nursery stock, and
propagative material
carrying various
pathogens increase the
development of
epidemics.
Cultural Practices
• Continuous
monoculture, large
acreages
• High levels of
nitrogen fertilization,
• No-till culture, dense
plantings
• Overheadirrigation,
• Injury by herbicide
application
• Poor sanitation
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16. List of Epidemic diseases
YEAR DISEASE LOCALITY
1845 Late blight of potato
(Phytophthora infestans)
Ireland
1870 Coffee rust
(Hemileia vastatrix)
Sri Lanka
1878 Downy mildew of
grapevine
(Plasmopara viticola)
France
1900 Lethal yellow of cocoa
(MLO)
Cuba
1904 Chestnut Blight
(Endothea parasitica)
America
1916 Wheat rust
(Puccinia tritici)
USA
Canada
1921 Bunchy top of Banana
(MLO)
Australia
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17. List of Epidemic diseases
YEAR DISEASE LOCALITY
1930 Sigatoka disease of banana
(Mycosphaerella musicola)
America
1936 Red rot of sugarcane
(Colletotrichum falcatum)
UP,India
1943 Brown spot of rice
(Helminthosporium oryzae)
West Bengal,India
1951 Bacterial blight
(Xanthomonas campestris)
Maharashtra
1969 Souther corn blight
(Helminthosporium maydis)
USA
1984 Apple scab
(Venturia inaequalis)
Jammu & Kashmir,India
1999 Rice tungro
(Tungro virus)
Punjab,India
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18. Management of epidemic
1. COMPUTER SIMULATION OF EPIDEMICS
2. FORECASTING PLANT DISEASE
EPIDEMICS
3. NEW TOOLS IN EPIDEMIOLOGY
4. DEVELOPMENT AND USE OF EXPERT
SYSTEMS IN PLANT PATHOLOGY
5. DISEASE-WARNING SYSTEMS
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19. COMPUTER SIMULATION OF
EPIDEMICS
• In a computer simulation of an epidemic, the
computer is given data describing the various
subcomponents of the epidemic and control
practices at specific points in time
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20. FORECASTING PLANT DISEASE
EPIDEMICS
1. Disease Diagnosis: The Key to Forecasting of any
Plant Disease Epidemic
2. Evaluation of Epidemic Thresholds
3. Evaluation of Economic Damage Threshold
4. Assessment of Initial Inoculum and of Disease
5. Monitoring Weather Factors That Affect Disease
Development
6. Forecasts Based on Amounts of Initial and
Secondary Inoculum
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21. NEW TOOLS IN EPIDEMIOLOGY
a. Molecular Tools
b. Geographic Information System
c. Global Positioning System
d. Geostatistics
e. Remote Sensing
f. Image Analysis
g. Information Technology
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22. DEVELOPMENT AND USE OF EXPERT
SYSTEMS IN PLANT PATHOLOGY
• Expert systems used frequently for diagnostic
purposes, i.e., identifying the cause of a
disease by the symptoms and related
observations.
• Expert system can advise growers of disease
potentials on the basis of the actual occurrence
of infection periods and provide pesticide
recommendations and suggestions for pesticide
amounts and timing of application.
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23. DISEASE-WARNING SYSTEMS
• The purpose of these systems is to warn
farmers of the impending onset of an
infection period or to inform them that an
infection period has already occurred so that
they can take immediate appropriate control
measures to stop recent infections from
developing or prevent further infections from
occurring
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24. CONCLUSIONS
• Plant diseases and epidemics cause a great
loss to agricultural production.
• Subsequently it affects the life of human and
livestock.
• Management, basically integrated disease
management shud be adopted to manage
disease and the loss due to them.
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25. REFERENCES
• PLANT PATHOLOGY, F i f t h E d i t i o n GEORGE N.
AGRIOS ,Department of Plant Patho
• Verreet, J. A., Klink, H., and Hoffmann, G. M. (2000).
Regional monitoring for disease prediction and optimization of
plant protection measures: The IPM wheat model. Plant Dis.
84, 816–826.logy,University of Florida,Amsterdam
• Wikipedia
• Leonard, K. M., and Fry, W. E., eds. (1986). “Plant Disease
Epidemiology,”Vol. 1. Macmillan, New York.
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