EPWS 310 - Plant Pathology
Lectures - Fall 2002
I. Plant Pathology - the study of plant diseases.
A. The study of Plant Pathology includes several aspects:
1) The biological entities and the environmental conditions that cause disease in plants
2) The mechanisms by which these factors produce disease in plants
3) The interactions between the disease-causing agents and the diseased plant
4) The methods of preventing or controlling disease and alleviating the damage it causes.
B. Why study plant pathology?
1. We dependent on plants for?
2. Damaged plants and products are damaged results in loss of life or lifestyle.
C. Plant pathologists' investigate plant disorders caused by:
Fungi, oomycetes, bacteria, viruses, viroids, nematodes, phytoplasmas, parasitic higher plants, protozoa, nutritional disorders
D. What is a plant disease?
Any disruption (biotic or abiotic) of the normal metabolism of a plant.
Agrios Page 5 - "the series of invisible and visible responses of plant cells and tissues to a pathogenic microorganism or environmental factor that results in adverse changes in the form, function, or integrity of the plant and may lead to partial impairment or death of the plant or it parts."
E. What is a pathogen?
An agent that induces disease.
F. How do pathogens cause disease?
1) Weakening the host
2) Killing or disturbing the metabolism of host cells
3) Blocking the transportation of food, mineral nutrients, and water
4) Directly consuming the contents of the host cells
G. Disease components.
Disease triangle. 1 2. 3.
All must be present for disease to occur.
H. Basic Terminology-
1. Symptoms- visible expression of disease.
2. Signs- physical presence of pathogen.
3. Etiology- study of the cause of a disease which may include the pathogen.
4. Epidemiology - study of populations in relation to disease.
I Significance of plant pathology.
*8000 fungi in North America cause 80,000 different diseases.
*180 species of bacteria
*500 different viruses cause plant diseases
*150 different nematodes
J. Crop losses due to plant diseases
Developing countries have a higher loss to disease, insects and weeds than developed countries.
Postharvest losses in developing countries are estimated at between 10-25%.
Over 40% of plant productivity in Africa and Asia and 20% in the developed world is lost to pests and pathogens. About one-third of the losses are due to viral, fungal, and bacterial pathogens.