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
Most important?
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.