clemson extension putting knowledge to work walker miller prof. emeritus agrisystems...
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Clemson Extension
Putting Knowledge to workWalker Miller Prof. Emeritus
Agrisystems productivity& ProfitabilityEconomic and community developmentEnvironmental ConservationFood safety & NutritionYouth Development& families
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
•Other Sponsors
Our objective todayMake a practioner out of you…Clemson has a Plant Problem ClinicAs a Master Gardener you will have contact w/clients that have plant problemsYou are the eyes and ears of the clinicYou are a vital link in communicationWith 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]
DiseaseAny 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
Plant Disease triangle
Susceptible host
Causal agentFavorable environment
Favorable Environment
Susceptible Host
HostA 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
ParasiteAny 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 PostulatesProof 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 PostulatesProof 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
SymptomsVisible 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
SymptomsVisible 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
FunctionVs.Symptom
SymptomsVisible 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 forwhat 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
• 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 asexualVariable in shape and sizeVariable in color and number of cells and variable in presentation
Reason for sex and hazard of cloning
Lets take a break !!
Infectious Disease Agents
• Fungi• Bacteria• Mollicutes – spiroplasmas & phytoplasmas• Viruses and viroids• Pirons – infective replicating proteins• Nematodes• Protozoan• Seed plants• Insects???
Stages in disease development
• Inoculation
• Penetration
• Infection
• Incubation
• Reproduction
• Dissemination
• Survival of adverse conditions
Diagnosing fungal diseases
• Symptoms
• Signs, morphology
• Culturing facultative pathogens
• Elisa immunoglobulin reactions
• PCR
Bacterial disease development
• Inoculation
• Passive entrance/ resident
• Multiply to threshold number
• Dissemination
• Survival
Bacterial diagnosis
• 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
• Inoculation
• Take over of cell DNA/RNA metabolism
• Replication
• Spread within plant
• Vector relationship
Viral diagnosis
• 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
• 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
SusceptibilityThe host fails to recognize an
invading pathogen ---therefore does not activate any resistance structural
or biochemical defenses
True resistancePathogen and host evolve together
Gene for gene relationship
Mono, oligo, polygenic
SAR
“Plantibodies”
Genetically Modified Plants
• Normal gene flow in the environment
• Transgenics• 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
• 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