This document provides an overview of crop diseases and their management. It discusses (1) the definition and objectives of plant pathology, (2) the historical development of the field including important contributors, and (3) the impact of plant diseases including common causes of crop losses. It also covers (3) classification of plant diseases, (4) the disease triangle concept of host, pathogen, and environment interactions required for disease development, and (5) common methods of plant disease control and management.

1. Crop Disease and their
management
PRESENTED BY – ANIMESH RAJ.

2. Plant Pathology (Phytopathology): -
The term plant pathology is derived from three Greek words: -
Phyton + Pathos + logos
Plant + suffering/diseases + study/knowledge
Definition: -
“Plant Pathology is that branch of agricultural, botanical or biological science
which deals with the study of the causes, etiology (infected form), resulting
losses, management and control of plant diseases.”

3. Objectives Of Plant Pathology
 To study the biotic, abiotic and environmental causes of plant diseases.
 To study the mechanism of disease development.
 To study the interaction between plant and pathogen.
 To develop the methods of plant disease management or control.

4. Historical Development Of Plant
Pathology
 Theophrustus (370-286 BC): -
He write a book entitled “Inquiry into Plants” .
He wrote the observations regarding diseases in this book.
 Julius Kuhn (1858): -
Write first book of Plant Pathology entitled.
“Disease of Cultivated Crops Their Causes And Their Control”
 T.J. Burril (1878): –
Reported first plant disease caused by bacteria entitled
“Fire Blight of Peach and Apple”
 Prof. Millaradet (1885): - Prepare first time “Bordeaux Mixture”
 Mayer (1886): – Worked on Tobacco Mosaic caused by Virus.

5. Plant Pathologist Of India
 E. J. Butler (1901-1920): –
First plant pathologist in India.
He wrote a book -“Fungi and disease in plant”.
He is known -“Father of Plant Pathology in India”
 D. D. Conninghum & A. Barclay: – Start study and identification of fungi.
 J. F.Dastur (1886-1971): -
First Indian Plant Pathologist.
He worked on Caster and Potato diseases caused by Phytophthora.

6. Impact Of Plant Disease
Losses caused by different pest in crops
PEST LOSS (%)
Weeds 33
Diseases 26
Insects 20
Storage pests 7
Rodents 6
Other’s 8
Total = 100%

7. Assessment of losses
 At least 10-30% of global food production
 Representing a threat to food security
 According to the report (2004) it is estimated that annual losses by
disease cost US$ 220 billion.

8. Pathogen: - “Any entity which can insite the disease is known as
pathogen”
Types of pathogenic microorganisms: -
(A). Biotic pathogens or Animate Causes: -
 Fungi
 Bacteria
 Phytoplasma or Spiro plasma
 Nematode (Worm)
 Algae
 Protozoa
 Parasitic Plants

9. (B). Mesobiotic causes: -
 Virus
 Viroid
 Prion
(C). Abiotic or Inanimate causes: -
a) Adverse climatic conditions: - Light, Temperature, Humidity, Rain, Hail,
Frost, Strom.
b) Adverse soil conditions: - Soli moisture, Structure, Nutrition, Texture,
Aeration, Soil pH.
c) Chemical Injuries: - Pollution, Pesticides.
d) Improper Cultural Practices: - Depth of sowing, Improper irrigation, Improper
fertilization, Improper harvesting.

10. Survival of Pathogen
Soil
Seed
Plant debris/ crop residues
Plants itself
Collateral Host
Alternate Host

11. Types of plant Diseases
Biotic plant disease
 Disease caused by fungi.
 Disease caused by prokaryotes
 Disease caused by parasitic plants and
green algae.
 Disease caused by virus and viroid‘s
 Disease caused by nematodes
 Disease caused by protozoan
A biotic plant disease
 Disease caused by too low and too high
temperature.
 Disease caused by lack of oxygen
 Disease caused by lack of sun light
 Disease caused by nutrients deficiency
 Disease caused by mineral toxicity
 Disease caused by toxicity of pesticide.

12. Disease Scenario
 Total Plant Diseases in the world - 80,000
 In India - 5,000 types of plant diseases
 Average disease per plant - 100

13. Classification of Plant Disease
1. According to affect on the host plant
(i) Localized diseases- Ex.- Rust of Wheat
(ii) Systemic Diseases-Ex.- Loose Smut of Wheat
2. According to symptoms & sign
(i). Smut (ii). Rust (iii). Mildew (iv).Wilt (v). Blight (vi). Canker
(vii). Root rot

14. 3. According to parts of the plant affected
(i) Root diseases: - Affect root of plants. Ex. -Root rot of vegetables
(ii) Stem diseases: - Affect stem of plants. Ex. -Stem gall of coriander.
(iii) Foliar disease: - Affect foliar parts of plants. Ex. –Leaf spot of Sorghum.
(iv) Fruit diseases: - Affect fruit of plants. Ex. -Fruit rot of Brinjal

15. 4. According to host plant affected
 Field crop diseases
 Vegetables crop diseases
 Fruit tree diseases
 Forest trees diseases
 Forage crop diseases
5. According to mode of perpetuation and spread
 Seed-borne diseases: - Ex.- Loose smut of wheat
 Soil-borne diseases: - Ex.- Sheath blight of rice
 Air-borne diseases: - Ex.- Rust of wheat

16. 6. According to occurrence
(i). Endemic disease
 These disease appear in a ‘Limited area’.
 Diseases appear ‘Every Year’.
 These do not cause ‘More Loss’
Ex. - Early blight of potato.
(ii). Epidemic or epiphytotic diseases
 These disease appear in a ‘Large Area’.
 Diseases appear ‘Periodically’.
 These diseases cause ‘More Loss’
Ex. - Late blight of potato

17. (iii). Sporadic diseases
 These diseases are ‘Sporadic’
 Appear on ‘Irregular Intervals’
 These diseases cause ‘Less loss than epidemic diseases’
Ex. - Powdery mildew of mango
(iv). Pandemic diseases
 These diseases appear in ‘Whole world/continent/ sub continent’
 Appear at ‘Periodic Intervals’
 These cause ‘Heavy Loss’
Ex. - Late blight of potato

18. The Disease triangle
Disease Development: -
The classic disease triangle establishes the conditions for disease
development, i.e. the interaction of a susceptible host, a virulent
pathogen and a favourable environment.

19. Plant disease triangle
No Disease
Environment
(Unfavorable)
Host
(Susceptible)
Pathogen
(virulent)

20. Plant disease triangle
No Disease
Environment
(Favorable)
Non‐Host
(Immune)
Pathogen
(Avirulent)

21. Plant disease triangle
Disease
Environment
(Favourable)
Host
(Susceptible)
Pathogen
(virulent)

22. Fungi:
10-15,000
Viruses:
~1,000
Nematodes:
several 100 sp.
Bacteria:
~100 sp.
Plant Pathogens

23. Plant disease control: -
Plant disease control
Immunization
Resistance Chemotherapy
Prophylaxis
Protection
Chemical Cultural
Eradication
Rotation Sanitation
Alternate host
eradication
Chemical
Legislation
Central State

24. “
”
End
THANKS