This document provides an introduction to the field of plant pathology by defining it as the study of plant diseases, their causes, and management. It discusses how plant pathology relates to other sciences and its key objectives, which include studying the etiology, pathogenesis, epidemiology, and control of plant diseases. The document emphasizes the importance of plant pathology, noting that diseases cause billions in annual crop losses worldwide. It provides examples of historical famines and epidemics caused by plant diseases. Finally, it outlines the broad scope of plant pathology in surveying, identifying, assessing, and developing management strategies for economically important plant diseases.

1. Introduction: Importance, scope
and objectives of plant pathology
HPP-5121
Fundaments of Plant Pathology

2. Meaning and Definition
• Phytopathology (Phyton : plant) Greek - Pathos (suffering)
+ Logos (study) = The study of the suffering plant
• Plant Pathology, also known as Phytopathology is a branch of
agricultural, biological or botanical science which deals with
the study of diseases in plants - their causes, etiology,
epidemiology, resulting losses and management.

3. Relation to other Sciences
• Plant pathology is related to many other sciences such as
virology,
mycology,
bacteriology,
microbiology,
physiology,
chemistry,
genetics,
biotechnology etc.,
all of which provide the knowledge required for the correct
diagnosis and management of plant diseases.

4. Objectives of Plant Pathology
1. Study of origin, causes or reasons. Study of living, non-living
and other causes of disease or disorder in plants- Etiology.
2. Study of mechanism of disease development i.e. processes of
infection and colonization of the host by the pathogen. This
phase involves complex host-pathogen interactions-
Pathogenesis

5. 3. study the interaction between the causal agent and the
diseased plants in relation to environmental conditions.
Generally at the population level- Epidemiology.
4. Development of management systems of the diseases land
reduction of losses caused by them- Control/ Management.

6. Importance of the Plant Diseases
• Globally, enormous losses of the crops are caused by the plant
diseases.
• The loss can occur from the time of seed sowing in the field to
harvesting and storage.
• About 34% of the crop produce is lost annually due to
diseases, insect-pests and weeds on the global basis (Cramer,
1967).

7. • When plant protection measures are not implemented, annual
loss of 30-50% are common in major crops including
horticulture (Encyclopedia Britannica, 2002).
Epidemics:
• Late blight of potato caused by Phytophthora infestans was
responsible for causing Irish famine in 1845 by destroying
the potato crop, the staple food of the people.
• Hundreds of thousand people died of hunger and disease, and
there was a large scale migration of the population to other
countries including North American continent.

8. • The population of Ireland was 8 million in 1940, which was
reduced to 4 million after the famine.
• This single disease forced man to realize the importance of
plant diseases, and brought the science of Plant Pathology to
lime light.
Other Famines:
• Wheat rust epidemics occurred from time to time in many
countries. Wheat rusts forced farmers to change their
cropping pattern and wheat was replaced by corn or maize or
rye.

9. • Brown spot of rice caused by Helminthosporium oryzae was
responsible for Bengal famine in 1943, which many people
think one of the reasons for the division of Bengal.
• Coffee rust caused by Hemileia vastatrix forced to cut down
the coffee plants in Sri Lanka in 1867.
• Powdery mildew of grapevines caused by (Uncinula
necator), by 1854, reduced the French wine production by 80
per cent.
• In 1878, the downy mildew caused by Plasmopara viticola
ultimately led to the discovery of Bordeaux mixture.

10. Losses in India:
• Wheat rusts cause a loss of Rs. 400 crore annually.
• In the years of epidemics, losses are Rs. 5000 crore or more.
• Loose smut of wheat is estimated to cause an average loss of 3
per cent (about Rs. 500 crore) every year.
• Other plant diseases such as red rot of sugarcane, potato
viruses, rice blast and blight, Karnal bunt of wheat, root knot
of tomato, eggplant and cucurbits, apple scab, mango
malformation, bunchy top of banana and sandal spike are
responsible for huge losses.

11. Effect on Society:
• Infected grains or the fruits may contain toxins (such as
aflatoxin, fumonosin) which cause insanity, paralysis, stomach
disorder and liver cancer.
• The money spent on the management of plant diseases is also a
loss because in the absence of diseases this money could be
saved.
• There are many other implications on the transport and agro-
based industry in the event of plant disease inflicted yield loss.
• There is restriction on the movements of food grains and other
agricultural produce due to the threat of quarantine pathogens
and pesticide residues in the produce causing further loss.

12. Scope of Plant Pathology
• Scope and responsibilities of plant pathology is unlimited.
• Its ultimate goal is to prevent and control plant diseases of
economic importance. Responsibilities of the science of plant
pathology may be summarized as under:
1. Survey of fields, orchards and areas in order to find out
prevalence of diseases and their incidence.
2. Recording new diseases of economic importance if any, with
their identification and extent of incidence.

13. 3. Assessment of losses caused by different diseases of economic
importance.
4. Study of etiology, symptoms, predisposing factors and
recurrence of such diseases.
5. Find out suitable and economic methods of management of
economically important plant diseases.
6. Assisting in breeding of disease resistant varieties.
7. To train the extension workers and subject matter specialists in
order to bridge the gap between pathologists and farmers for
better crop production.