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Introduction to Plant Pathology:Introduction to Plant Pathology:A Master Gardener Short Course
David Doll
Farm Advisor, Merced County
What is Plant Pathology?What is Plant Pathology?
St d f Pl t DiStudy of Plant Diseases:– Biotic, or living diseases– Abiotics disorders, or non‐,
infectious diseases– Sometimes referred to as
PhytopathologyPhytopathologyHow Important?
– $220 billion crop value loss h d t dieach year due to diseases
alone – Does not include
i i i h hinteractions with other organisms
What is Plant Pathology?What is Plant Pathology?
An Interdisciplinary field:‐ Biology, horticulture, mycology, bacteriology, virology, plant physiology, entomology etcentomology, etc.
Benefits from advances in‐ Benefits from advances in any other science
What is Plant Pathology?What is Plant Pathology?
A Reactive Field:– Plant can not communicate with us
– No curatives for plant di (f ti )diseases (few exceptions)
– Either live with losses or prevent with culturalprevent with cultural practices
What is Plant Pathology?
A hi i l fi ld
What is Plant Pathology?
A historical field:– Studied since the advent of farming firstof farming – first recorded by the Greeks
– Field first defined in 1861 with the identification of the Potato Late BlightPotato Late Blight Pathogen
– Modern Plant Pathology gycombines Molecular and Field techniques
Historical Review of Plant PathologyHistorical Review of Plant Pathology
• Robert Hooke ‐ 1670
• Carl van Linne ‐ 1735
• Antonio Leeuwenhoek ‐16741674
• Charles Darwin ‐ 1859
A t d B 1861• Anton deBary – 1861
• Louis Pasteur – same time
• Robert Koch ‐ 1887
Koch’s PostulatesKoch s Postulates
1 O i t b1. Organism must be present in all plants showing symptoms.g y p
2. Agent must be isolated from diseased hosts
3 Th l i3. The pure culture is inoculated into a healthy host
4. The disease is reproduced
5. The same causal agent is re‐isolated from host
What is a healthy/diseased plant?What is a healthy/diseased plant?
Healthy Plant1. Carries out its
Diseased Plant1. When the ability of cells of
physiological functions to the best of its genetic
t ti l
a plant or plant part is compromised
potential
2. Cells divide and differentiate as needed
‐ Biological agent
‐ Environmental factor
2 Cells affected indicatesdifferentiate as needed and specialized cells fulfill dedicated tasks
2. Cells affected indicates type of physiological function lost.ded cated tas s u ct o ost
Causes of Plant DiseasesCauses of Plant Diseases
Bi l i l A t• Biological Agents
1. Fungi2. Viruses3. Bacteria
d4. Nematodes5. Parasitic Plants6 Viroids6. Viroids7. Protozoans
Biotic Disease – Disease symptom caused by a y p y“living” organism
Agrios, 2005
Causes of Plant Diseases
E i l F
Causes of Plant Diseases
• Environmental Factors1. Temperature2. Moisture3. Inadequate Oxygen4 Li ht4. Light5. Air Pollution6 Nutritional Deficiencies6. Nutritional Deficiencies7. Herbicide Injuries
Abiotic disorder/noninfectious disease – Disease symptom caused by ancaused by an environmental factor.