Introduction
to plant pathology
What is a plant disease
A
plant disease is any abnormal condition that alters the appearance or function
of a plant. It is a physiological process that affects some or all plant
function. Disease may also reduce yield and quality of harvested product.
Disease is a process or a change that occurs over time. It does not occur
instantly like injury. Visible effects of disease on plants are called Symptom- any detectable change in color
and Sign – physical evidence of the pathogen.
What cause plant disease
Infectious
plant disease is caused by living organisms that attack and obtain their
nutrition from the plant they infect. The parasitic organisms that cause a
disease is a pathogen.
Type of pathogen
-
Fungi
-
Bacteria
-
Viruses
-
Nematode
Role of environment
A
favorable environment is critically important for disease development- even the
most susceptible plant exposed to huge amounts of a pathogen will not develop
disease unless environmental conditions are favorable.
Groups of plant pathogens
-vast
majority are beneficial
-Can
cause plant, human, and livestock disease
-
Most cannot be seen without a microscope
Bacteria
-Extremely
small organism
-Population
can increase in short period of time
-Cells
clump together in masses called colonies
Viruses
-Most familiar because they cause
human and animal disease,
such as in influenza
-Cause
some destructive plant disease.
-Survive
only in living cells.
Nematode
-Round slander, threadlike worm
-Some
are parasites on animal, insects,
fungi, other nematode and plant
-Most
live in the soil and feed in or on plant roots
How pathogen survival
-
Soil
-
Crop
residue
-
Weed
or non-crop host
-
Seed
or vegetative plant parts
-
Insects
-
Mild
climate.
Reference.
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