Transcript mg_plantpath_miller

Clemson Extension
Putting Knowledge to work
Walker Miller Prof. Emeritus
Agrisystems productivity& Profitability
Economic and community development
Environmental Conservation
Food safety & Nutrition
Youth Development& families
•Other Sponsors
The Happy Berry Inc and
Happy Berry Consulting
Walker Miller, Plant Pathologists
Professor Emeritus Clemson
University, Certified Crop Advisor
#18472, SC Licensed Pesticide
Applicator #1063, Owner & operator
of The Happy Berry Inc
Our objective today
Make a practioner out of you…
Clemson has a Plant Problem Clinic
As a Master Gardener you will have
contact w/clients that have plant problems
You are the eyes and ears of the clinic
You are a vital link in communication
With experience you will make your
own diagnosis
Our objective
To help you integrate what you have learned
or will learn about soils, insects, horticulture
into a process that will enable you to become
a Master Gardener to help others solve their
plant problems
Vocabulary is the key to communication
Plant Pathology
The Study of Plant Disease
[pathos – suffering]
[ology – study of]
Disease
Any deviation from normal growth,
structure or function of a plant that is
a continuous condition which
produces visible symptoms, thus
affecting the economic quality or
value of that plant.
The three must have items for
disease to occur
Susceptible host
Favorable
Causal agent
environment
Plant Disease triangle
Favorable
Environment
Susceptible
Host
Host
A plant species that
provides some or all of the
nutrients for a particular
plant species
Virulent
Pathogen
Pathogen
Any agent of causing
a plant disease
Parasite
Any organism that reside in or on another
organism and derives some or all of its
nutrients from the host organism. Parasites
can be either obligate [surviving only in or on
a living organism] or facultative [surviving on
live or dead organisms].
All pathogens are parasites but not all parasites are pathogens
Saprophyte
An organism that derives all
of its nutrients from dead
organic matter as contrasted
to a parasite that lives in or
on living tissue
Facultative Saprophyte – Is a
parasite that has the faculty to
live as a saprophyte
Facultative Parasite - Is a
saprophyte that has faculty
to live as a parasite
Fungal pathogens range obligate saprophyte to obligate parasite
Koch’s Postulates
Proof of Pathogenicity
• The pathogen must be constantly
associated with the disease
• The pathogen must be isolated and
grown in pure culture and
characterized
Koch’s Postulates
Proof of Pathogenicity
• The isolated pathogen must cause the
identical disease in inoculated plants of
the same variety
• The pathogen must be isolated from
inoculated plants and be identical to
the original isolate
Infectious Disease
A disease that can be spread
from one plant to another
since it is caused by living
organism
Agents of Disease
Noninfectious plant disease
A disease incapable of being spread
from plant to plant since it is caused
by non-living environmental factors
More common than infectious
Genetic diseases
Injury
Damage to a plant by some factor
[insect, (?) wind, hail, machinery]
that occurs over a short period of time
rather developing in a continuous
sense as with disease.
Non Infectious Disease Agents
• Nutrient imbalance
• Temperature [incident vs.
imbalance]
• Water imbalance
• Light imbalance
Symptoms
Visible or measurable expression of
disease by a plant
Symptoms
Visible or measurable expression of disease by a
plant
Leaf blight – sudden deaf of tissue
Leaf spot – localized death of tissue
Fruit rot - disintegration
Wilt – interference with water movement
Galls – cancerous growths
Cankers – depressed elliptical areas
Root rot – disintegration
Symptoms
Visible or measurable expression of disease
by a plant can be classified
• Necrosis – rots, spots, blights
• Reduction photosynthesis
• Yield
• Yellowing vs. chlorosis
• Disruption of translocation
• Localized – spots, blights, galls, cankers
• Systemic – dieback, decline, stunting, wilt
Function
Vs.
Symptom
Symptoms
Visible or measurable expression of disease
by a plant can be classified
The point is interpretation- symptoms give you clues
as to what agent of disease might be, where to look for
what the problem is, what samples to collect…
Signs
The obvious presence of a pathogen
in the form of spores, mycelia,
sclerotia, bacterial ooze, fruiting
structure etc.
Is there any sign (s) of the pathogen (s) present on
the plant ?
Pathogen signs
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Mycelia
Ooze
Fruiting bodies
Rusts
Sclerotia
Mushrooms
Conidiophores and spores
Spore
The fungal structure analogous to a
seed in higher plants. It serves to
reproduce and spread the fungus.
Sexual or asexual
Variable in shape and size
Variable in color and number of cells
and variable in presentation
Reason for sex and hazard of cloning
Lets take a
break !!
Infectious Disease Agents
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Fungi
Bacteria
Mollicutes – spiroplasmas & phytoplasmas
Viruses and viroids
Pirons – infective replicating proteins
Nematodes
Protozoan
Seed plants
Insects???
Stages in disease development
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Inoculation
Penetration
Infection
Incubation
Reproduction
Dissemination
Survival of adverse conditions
Diagnosing fungal diseases
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Symptoms
Signs, morphology
Culturing facultative pathogens
Elisa immunoglobulin reactions
PCR
Bacterial disease development
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Inoculation
Passive entrance/ resident
Multiply to threshold number
Dissemination
Survival
Bacterial diagnosis
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Symptoms
Morphology and staining
Growth on substrates or lack of
Enzyme activity or lack of
Hypersensitive reactions
ELISA/immunoglobulin assays
Fatty acid profiles
PCR probes
Viral disease development
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Inoculation
Take over of cell DNA/RNA metabolism
Replication
Spread within plant
Vector relationship
Viral diagnosis
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Symptoms
Inclusion bodies and electron microscopy
Host range studies
Non host reactions / hypersensitivity
Elisa/immunoglobulin
PCR
Diagnostic procedures can be very expensive
Principles of Disease
Management
• Exclusion
• Quarantine, certified propagules, protective coverings
and environmental manipulation
• Eradication
• Crop rotation, surgery, sanitation
• Protection
• Plant pharmaceuticals, Direct…cides bio & non bio, Indirect SAR,
vector control
• Resistance
• Non host, true resistance and apparent resistance
Environmental manipulation
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Arid area seed production
Proper time &depth of planting
Avoidance of wet soils – raised beds
Proper plant spacing, orientation &air
drainage
• Manipulating green house vents
Sometimes given a special category of cultural control
Susceptibility
The host fails to recognize an
invading pathogen ---therefore does
not activate any resistance structural
or biochemical defenses
True resistance
Pathogen and host evolve together
Gene for gene relationship
Mono, oligo, polygenic
SAR
“Plantibodies”
Genetically Modified Plants
• Normal gene flow in the environment
• Transgenics
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Within species - Marker assisted breeding
Across species - ditto
Across genera and families
Across kingdoms
The Plant Problem Clinic
•Service
•Education
•Research
Service
• Diagnosis – takes dollars and time
• Control recommendations
• Electronic technology to to speed response
• Agents trained to send specimens via the web
• Shared with specialist across the state and
around the country/world where needed
• Prompt reply once diagnosis is confirmed
Form a
diagnostic
hypothesis
What evidence is
needed to confirm
that hypothesis?
Confirm or deny
the hypothesis
If hypothesis can not be
confirmed or denied --present as hypothesis
not fact
The cost
consideration
Balance the cost of diagnosis with
risk exposure and or willingness to
pay
Education
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County agent training
Master gardener training
Student education
Support Home Garden Center
Landscape industry training
Annual and other reports
Research
• Detect new diseases
• A vital link in homeland security
• Cooperate regionally, nationally and
internationally
• Maintain database of pathogens
• Evaluate new techniques
• Support disease management research
• Apply research to the regulatory process
Thank you for this opportunity!
Questions Discussion
Please visit us at The Happy Berry in
Six Mile
Or on the web at
www.thehappyberry.com