Plant production is reduced significantly every year, due to pathological problems. To control these problems is to increase productivity, and for the horticultural business that means increased profit margins.
PLANT PATHOLOGY IS NOT simply a study of pests and diseases. Some pests are in fact not pathological problems, and there are pathological problems which are not pests or diseases.
PLANT PATHOLOGY is about problems in plants caused by physiological damage or irritation at a cellular level. It is concerned with problems which affect parts of the plant cell, leading to malfunctions in the normal processes which occur within the plant.
Lesson Structure
There are 8 lessons in this course:
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Introduction
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Overview of plant disease
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Diagnosis of problems: nutritional, environmental, pathological
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Symptoms
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Common terminology
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Types of Diseases
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Morphological changes
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Necrosis
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Hypoplasia's
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Hyperplasia
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Types of pathogens: viruses, bacteria, actinomycetes, fungi, nematodes
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Techniques for diagnosing plant diseases: optical equipment, preparing pathogens for observation, culture methods, inoculation, etc
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Plant viruses; detection and diagnosis
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Plant nematodes
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Case study: Australian plant nematodes
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Main types of diseases
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Spots
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Rots
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Cankers
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Galls
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Mildews
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Rusts
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Moulds
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Wilts
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Scabs
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Others
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Using a key to diagnose diseases in plants
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The Lifecycle of a Disease
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Inoculation
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Penetration
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Infection
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Growth and reproduction
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Dissemination
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Methods of penetration by bacteria and nematodes
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Lifecycle of nematodes
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Fungal biology
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Role of insect spreading fungal and bacterial pathogens
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Control Techniques
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Sanitation
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Resistant Plant Varieties
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Biological Controls
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Soil Drenches/dips
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Chemical Controls
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Nematicides
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Soil fumigants
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Contact poisons
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Fungicides and the environment
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Systemic fungicides
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Misters, dusters, blowers, sprayers
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Spray maintenance and cleaning
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Natural controls: cultural, physical, biological, etc
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Terminology
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Selected Pathogen Diseases Ornamentals
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Fungi affecting turf
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Phytophthora cinnamomi
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The process of tree decay: Shigo
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Case study: how phytophthora cinnamomi kills a susceptible Eucalyptus
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Peach powdery mildew
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Rose powdery mildew
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Honey fungus on rhododendrons and azaleas
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Petal blight on rhododendrons and azaleas
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Selected Pathogen Diseases Crops
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Sclerotinia rot in vegetables
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Nematodes and citrus production
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Citrus diseases: scaly butt, lemon crinkle, citrus canker
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Brown rot
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Fire blight
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Apple fruit rot caused by trichoderma harzianum
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Prunus necrotic ringspot virus in cut flower roses
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Potato and tomato blight
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Club root
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Non-Infectious Diseases
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Nutritional disorders
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Lack of water
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Excess water
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Other environmental problems
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Disorders caused by man: mechanical damage, pollution
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Case Study: Air pollution
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Other disorders: genetic, disturbed growth
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Non parasitic turf problems
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Special Project
Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.
Aims
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Describe a range of pathological problems that affect plants.
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Describe symptoms of a range of diseases that affect plants.
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Describe disease life cycles and explain how this knowledge can be applied in disease control
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Explain the methods used to control diseases
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Demonstrate a comprehensive knowledge of a particular plant pathogen.
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Identify and describe a range of non-infectious diseases and problems that affect plants
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Identify and describe a range of common pathogens that affect ornamental plants.
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Identify and describe a range of common pathogens that affect crop plants
What You Will Do
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The first part of the course develops an understanding of the different types of problems which can occur and how to identify them.
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Terminology is covered in some depth, so as to enable the student to be able to read & understand books & articles written about plant diseases. Other major topics of study include "symptoms" (ie: Necroses, Hypoplasia, etc), "types of pathogens" (ie: Viruses, bacteria, fungi, Nematodes, etc), and the lifecycle of a disease.
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The second part of the course looks at how to control pathology problems. The major methods of controlling pathogens (ie: Sanitation, resistant varieties, biological controls, soil drenches & chemical sprays, etc) are all studied, along with types of equipment & safety.
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The third part of the course looks at some of the most common plant pathology problems in commercial horticulture, how to identify them and how they are controlled.
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Some of the problems studied include cinnamon fungus, tree decay, powdery mildew, nematodes, brown rot, blights, turf fungi, damping off and non infectious problems such as temperature burns, air pollution, wind burn and excessive light.
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The course is a highly practical one involving as much time in practical/field work as it does theory.
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No prior formal training is required, though anyone undertaking this course is expected to have some experience in horticulture (either having worked in the industry or having studied in some related discipline.
TYPES OF DISEASES
MORPHOLOGICAL SYMPTOMS
Necroses refers to death of parts of, or whole plants. Normally protoplasts degenerate, followed by the death of cells.
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Plesionecrotic ‑term to describe cells which are almost dead.
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Holonecrotic ‑term used to describe cells which are completely dead.
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Plesionecroses ‑yellowing, wilting or hydrosis (ie: very wet tissue), are common plesionecrotic conditions.
Yellowing is seen when chlorophyll breaks down. (This is different to chlorosis ‑ chlorosis is when chlorophyll does not develop in the first place). Though yellowing and chlorosis are often used as interchangeable terms, they are in fact distinctly different.
Wilting involves drooping of plant parts, caused by a loss of turgor (ie: pressure) within the cells. Wilting can be due to either:
Hydrosis ‑tissue becomes water soaked, cell membranes have been broken and liquid released...this often preceedes fungal rots, spots or blight.
Holonecroses
Browning or blackening of part of a diseased plant....sections of tissue die completely....can occur in any part of a diseased plant.
There are three main types of holonecroses....
a/ Necroses of Storage Organs
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Occurring in fruit, seed, bulbs, corms, rhizomes, tubers and roots
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Frequently (but not always) hydrosis, followed by a blackening of tissue and eventually rot.
b/ Necroses of Green Plant Tissue
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Typical examples include damping off, spot diseases (where spots of tissue die), streak diseases where streaks of tissue die, etc.
c/ Necrosis of Woody Parts
Hypoplases
Failure of plant parts to develop fully (eg: Dwarfing, rosetting, etiolation, mosaic, etc.).
Hyperplases
This refers to abnormal development of plant parts, or overdevelopment of the entire plant.
Includes:
Gigantism.....eg: Curl of leaves or shoots, club root, fasciation.
Hyperchromes....Development of abnormal colour eg: Bronzing, virescence (chlorophyll where it doesn't normally occur).
Metaplasia....Where a plant part changes to another type of plant part, which it should not be (eg: part of a flower developing a leaf like structure).
Prolepsis....Premature development of plant parts. eg: a shoot starting to grow from a bud prematurely, then dying back.
How this Course Might Benefit You
Plant
diseases affect all sorts of plants from crops through to cultivated ornamental
species and native plants. Sometimes we can live with those diseases but at
other times they may destroy our livelihoods, or our prized plants. Anyone who
works with plants will have witnessed just how devastating diseases can be.
This course goes into significant depth into the major recognised groups of
diseases. It also examines the life cycles and course of some particular
diseases of economic concern. Students of this course will have a great
understanding of plant diseases that should set them in good stead for
recognition of symptoms and diagnosis.
This
course is ideally suited to people working in, or aspiring to work in:
- Horticultural
science
- Horticulture
research
- Agronomy
- Horticultural
consultation
- Teaching
- Crop
growing
- Fruit
& vegetables
- Botanic
gardens
- Parks
& gardens
- Garden
maintenance
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