Introduction to Plant Pathology: A Master Gardener Short Course

David Doll Farm Advisor, Merced County Part 1: Principles of Plant Pathology What is Plant Pathology?

Stu dy of Plan t Diseases: – Biotic, or living diseases – Abiotics disorders, or non‐ infectious diseases – Sometimes referred to as Phytopathology How Important? – $220 billion crop value loss each year due to diseases alone – Does not include iiinteractions wiihth other organisms What is Plant Pathology?

An Interdisciplinary field: ‐ Biology, horticulture, mycology, bacteriology, virology, plant physiology, entomology, etc.

‐ Benefits from advances in any other science What is Plant Pathology?

A Reactive Field: – Plant can not communicate with us – No curatives for plant diseases (few exceptions ) – Either live with losses or prevent with cultural practices What is Plant Pathology?

A histor ica l fie ld: – Studied since the advent of farming – first recorded by the Greeks – Field first defined in 1861 with the identification of the Potato Late Blight Pathogen – Modern Plant Pathology combines Molecular and Field techniques Historical Review of Plant Pathology

• Robert Hooke ‐ 1670 • Carl van Linne ‐ 1735 • Antonio Leeuwenhoek ‐ 1674 • Charles Darwin ‐ 1859 • AtAnton dBdeBary – 1861 • Louis Pasteur –same time • Robert Koch ‐ 1887 Koch’ s Postulates

1. OiOrganism must be present in all plants showing syypmptoms. 2. Agent must be isolated from diseased hosts 3. 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?

Healthy Plant Diseased Plant 1. Carries out its 1. When the ability of cells of physiological functions to a plant or plant part is the best of its genetic compromised pottiltential ‐ Biological agent 2. Cells divide and ‐ Environmental factor differentiate as needed 2. Cells affected indicates and specialized cells fulfill type of physiological dedicated task s fuuctonction lost. What is a healthy/diseased plant?

Agrios, 2005 Causes of Plant Diseases

• Bio log ica l AAtgents 1. Fungi 2. Viruses 3. Bacteria 4. Nematodes 5. Parasitic Plants 6. Viroids 7. Protozoans

Biotic Disease – Disease syypmptom caused by a “living” organism

Agrios, 2005 Causes of Plant Diseases

• EiEnvironmenta l Factors 1. Temperature 2. Moisture 3. Inadequate Oxygen 4. Lig ht 5. Air Pollution 6. Nutritional Deficiencies 7. Herbicide Injuries

Abiotic disorder/noninfectious disease –Disease symptom caused by an environmental factor.