Clemson Extension

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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
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The Happy Berry Inc and Happy Berry Consulting

• Other Sponsors

• Walker Miller, Plant Pathologists Professor
  Emeritus Clemson University, Certified Crop
  Advisor 18472, SC Licensed Pesticide Applicator
  1063, Owner operator of The Happy Berry Inc

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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

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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
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Plant Pathology

• The Study of Plant Disease
• pathos suffering
• ology study of

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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.

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The three must have items for disease to occur
Susceptible host
Favorable environment
Causal agent
Plant Disease triangle
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Favorable Environment
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Susceptible Host
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Host

• A plant species that provides some or all of the
  nutrients for a particular plant species

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Virulent Pathogen
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Pathogen

• Any agent of causing a plant disease

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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
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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
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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
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Kochs PostulatesProof of Pathogenicity

• The pathogen must be constantly associated with
  the disease
• The pathogen must be isolated and grown in pure
  culture and characterized

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Kochs 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

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Infectious Disease

• A disease that can be spread from one plant to
  another since it is caused by living organism

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Agents of Disease
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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
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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.

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Non Infectious Disease Agents

• Nutrient imbalance
• Temperature incident vs. imbalance
• Water imbalance
• Light imbalance

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Symptoms

• Visible or measurable expression of disease by a
  plant

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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
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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

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Function Vs. Symptom
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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 for
• what the problem is, what samples to collect

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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 ?
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Pathogen signs

• Mycelia
• Ooze
• Fruiting bodies
• Rusts
• Sclerotia
• Mushrooms
• Conidiophores and spores

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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
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Lets take a break !!
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Infectious Disease Agents

• Fungi
• Bacteria
• Mollicutes spiroplasmas phytoplasmas
• Viruses and viroids
• Pirons infective replicating proteins
• Nematodes
• Protozoan
• Seed plants
• Insects???

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Stages in disease development

• Inoculation
• Penetration
• Infection
• Incubation
• Reproduction
• Dissemination
• Survival of adverse conditions

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Diagnosing fungal diseases

• Symptoms
• Signs, morphology
• Culturing facultative pathogens
• Elisa immunoglobulin reactions
• PCR

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Bacterial disease development

• Inoculation
• Passive entrance/ resident
• Multiply to threshold number
• Dissemination
• Survival

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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

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Viral disease development

• Inoculation
• Take over of cell DNA/RNA metabolism
• Replication
• Spread within plant
• Vector relationship

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Viral diagnosis

• Symptoms
• Inclusion bodies and electron microscopy
• Host range studies
• Non host reactions / hypersensitivity
• Elisa/immunoglobulin
• PCR

Diagnostic procedures can be very expensive
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Principles of Disease Management

• Exclusion
• Quarantine, certified propagules, protective
  coverings and environmental manipulation
• Eradication
• Crop rotation, surgery, sanitation
• Protection
• Plant pharmaceuticals, Directcides bio non
  bio, Indirect SAR, vector control
• Resistance
• Non host, true resistance and apparent resistance

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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
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Susceptibility

• The host fails to recognize an invading pathogen
  ---therefore does not activate any resistance
  structural or biochemical defenses

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True resistance

• Pathogen and host evolve together
• Gene for gene relationship
• Mono, oligo, polygenic
• SAR
• Plantibodies

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Genetically Modified Plants

• Normal gene flow in the environment
• Transgenics
• Within species - Marker assisted breeding
• Across species - ditto
• Across genera and families
• Across kingdoms

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The Plant Problem Clinic

• Service
• Education
• Research

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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

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Form a diagnostic hypothesis
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What evidence is needed to confirm that
hypothesis?
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Confirm or deny the hypothesis
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If hypothesis can not be confirmed or denied
---present as hypothesis not fact
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The cost consideration

• Balance the cost of diagnosis with risk exposure
  and or willingness to pay

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Education

• County agent training
• Master gardener training
• Student education
• Support Home Garden Center
• Landscape industry training
• Annual and other reports

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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

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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