1. INTRODUCTION TO PLANT PATHOLOGY
CHAPTER 1
INTRODUCTION
TO PLANT PATHOLOGY

2. Objectives To define plant pathology To define plant disease
To classify plant diseases
To identify the main causal agent of plant disease

3. Plant Pathology Also be referred as ‘Phytopathology’
A science that study plant disease
The diseases are caused by pathogens (infectious diseases) and environmental conditions (physiological factors)
Improve the chances of plant survival

4. What is actually plant disease?

5. ‘A malfunctioning process that is caused by continuous irritation and produce symptoms’ Horsfall & Cowling ‘A deviation from normal growth or structure of plants that is sufficiently pronounced and permanent to produce visible symptoms or to impair quality and economic value’ Stakman & Harrar

6. Healthy plant : The ability to carry out normal physiological functions at a acceptable level consistent to genetic potential Sick plant : A malfunctioning process that is caused by continuous irritation and produce symptoms

7. Healthy Plant

8. Healthy Plant Normal physiological functions include:
Normal cell division, differentiation & development
Absorption of water and minerals from the soil and translocation
Photosynthesis and translocation of photosynthates
Utilization and storage of photosynthates
Reproduction
Storage of reserves for overwintering or reproduction.

9. Diseased Plant A plant would not have all of these at once
Plant disease is any disruption (biotic or abiotic) of the plants normal metabolism.

10. “ The malfunctioning of host cells and tissues that results from their continuous irritation by a pathogenic agent or environmental factor and leads to the development of symptoms.
Disease in a condition involving abnormal changes in the form, physiology, integrity, or behavior of the plant.
Such changes may result in partial impairment or death of the plant or its parts”
George N. Agrios

11. Classification of plant disease
Infectious
Non-infectious

12. Infectious Disease
A disease that is caused by a pathogen that can spread from a diseased to healthy plant
Disease that is caused by living organism

13. Non-infectious Disease
Disease that is caused by non living organism
Could not be spread to other healthy plant
Example factors:
Too low/high temperature
Lack/excess of soil moisture
Air pollution
Nutrient deficiencies
Mineral toxicities
Soil acidity or alkalinity

14. Causes of plant disease
Biotic factors - any living factors that could cause disease
Fungi
Bacteria
Virus
Nematodes

15. Causes of plant disease
Abiotic factors - any non-living factors that could cause disease
Nutrient deficiencies
Toxicities
Environmental stress ( drought; heat; cold )