Diseases of various Plants

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    PLANT DISEASE

    OrPlants Do Get Sick

    John F. Baniecki, Ph.D.

    Extension Specialist and Professor

    West Virginia University

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    WHAT IS A PLANT DISEASE?

    A plant disease may be defined asany disturbance that prevents the

    normal development of a plant and

    reduces its economic or aestheticvalue.

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    ASSOCIATED WITH A DISEASE ARE:

    SYMPTOMS

    SIGNS

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    A

    SYMPTOM

    The visible response of a plant to acausal agent over time.

    May be caused by:living agents (Biotic)

    non-living agents (Abiotic)

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    PLANT DISEASE SYMPTOMS

    Produced by non-living agents(Abiotic)

    Environmental

    Chemical

    Nutritional

    Cultural

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    PLANT DISEASE SYMPTOMS

    EnvironmentalCold

    Heat or DroughtLightning

    Wetness

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    PLANT DISEASE SYMPTOMS

    Environmental

    Cold------------Brrrrrrrrrr!

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    PLANT DISEASE SYMPTOMSEnvironmental

    Heat or Drought

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    PLANT DISEASE SYMPTOMS

    Environmental

    Lightning Damage

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    PLANT DISEASE SYMPTOMS

    Environmental

    Wetness Results: Root Rot

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    PLANT DISEASE SYMPTOMS

    Chemical

    Salt Fertilizer Pesticide

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    PLANT DISEASE SYMPTOMS

    Nutritional

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    PLANT DISEASE SYMPTOMS

    CulturalTree Girdling

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    PLANT DISEASE SYMPTOMS

    CulturalOverwatering

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    PLANT DISEASE SYMPTOMS

    Produced by Living Agents (Biotic)

    Fungi

    BacteriaViruses, Viroids, Mycoplasmas

    SpiroplasmsNematodes

    Parasitic Vascular Plants

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    PLANT DISEASE SYMPTOMS

    Fungi

    Lower forms of plant life

    Microscopic thread-like growthLack chlorophyll

    Attack higher forms of plant lifeSpread by wind, rain, insects

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    PLANT DISEASE SYMPTOMS

    Fungi

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    PLANT DISEASE SYMPTOMS

    Fungi cause:

    Leaf spots or BlotchesBlight

    Cankers

    Root rot

    Wilt and/or reduced growth, death

    Trunk rot

    Abnormal growth or galls

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    PLANT DISEASE SYMPTOMS

    BacteriaSingle celled organisms

    Enter the plant through naturalopenings or plant injuries

    Spread by wind, rain, insects

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    PLANT DISEASE SYMPTOMS

    Bacteria Streaming from a plant

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    PLANT DISEASE SYMPTOMS

    Bacteria cause:

    Leaf spots or BlotchesBlight

    Cankers

    Root rot

    Wilt and/or reduced growth, death

    Abnormal growth or galls

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    PLANT DISEASE SYMPTOMS

    VirusesSubmicroscopic, replicate inside

    living cells

    Composed of a piece of genetic

    material (either RNA or DNA)

    surrounded by a protein coatTakes over the plant cell metabolism

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    PLANT DISEASE SYMPTOMS

    VirusesGain entry to cells through a wound or

    during insect feeding

    Spread by man and insects

    Occurs in weeds and other plants

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    PLANT DISEASE SYMPTOMS

    VirusesCan be maintained in a population of

    plants or

    transferred from plant to plant by:

    vegetative propagation

    grafting

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    PLANT DISEASE SYMPTOMS

    VirusesCan also be maintained or transferred by:

    dodder, a parasitic plant

    mechanically in sap on hands, tools,

    ropes, etc.

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    PLANT DISEASE SYMPTOMS

    Viruses

    Can also be maintained or transferred

    by:

    feeding by nematodes, mites, aphids,

    leaf hoppers, thrips, and whiteflies

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    PLANT DISEASE SYMPTOMS

    Viruses

    Can also be maintained:

    on or inside seeds

    in pollen

    in certain root-infecting fungi

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    PLANT DISEASE SYMPTOMS

    Viruses Tobacco Mosaic Virus

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    PLANT DISEASE SYMPTOMS

    Viruses cause:Dead areas on leaves

    Abnormal growthReduced growth, death

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    PLANT DISEASE SYMPTOMS

    Viroids

    Piece of genetic material

    Has no protein coatDivert plant metabolism to

    produce more viroids

    Spread by vegetative

    propagation

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    PLANT DISEASE SYMPTOMS

    Potato spindle tuber viroid

    Short, upright, stunted growth

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    PLANT DISEASE SYMPTOMS

    Mycoplasmas, Spiroplasms, andPhytoplasms

    Similar to bacteriaHave no cell wall

    Found in the infected plant water-

    and food- conducting vesselsLeaf hoppers transmit mycoplasmas

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    PLANT DISEASE SYMPTOMS Mycoplasmas, Spiroplasms, and

    Phytoplasms

    cause:

    Growth abnormalitiesYellowing

    Short internodes

    Distortion of leaf and flower tissue

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    PLANT DISEASE SYMPTOMS

    Stubborn disease of citrusSpiroplasma

    Uneven fruit size, reduction

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    PLANT DISEASE SYMPTOMS

    Carrot aster yellows phytoplasm

    Yellowing of foliage, hairy rootsand internal root necrosis

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    PLANT DISEASE SYMPTOMS

    NematodesMicroscopic worms

    Found in the soilOccurs in weeds and other plants

    Spread by man

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    PLANT DISEASE SYMPTOMS

    Nematodes

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    PLANT DISEASE SYMPTOMS

    Nematodes cause:Abnormal growth or galls

    Reduced growth, death

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    PLANT DISEASE SYMPTOMS

    Parasitic vascular plantsDodder, mistletoe, witchweed,Indian pipes, beech drops

    Gain nutrients by parasitizing seed-

    bearing plants

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    PLANT DISEASE SYMPTOMS

    Parasitic vascular plantsDodder

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    PLANT DISEASE SYMPTOMS

    Parasitic vascular plantsMistletoe

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    PLANT DISEASE SYMPTOMS

    Parasitic vascular plantsWitchweed

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    PLANT DISEASE SYMPTOMS

    Parasitic vascular plantsIndian pipes

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    PLANT DISEASE SYMPTOMS

    Parasitic vascular plantsBeech drops

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    PLANT DISEASE SYMPTOMS

    Wilts

    Rots

    Root Rot Blights

    Leaf Spots or Blotches

    Cankers Growth or Galls

    Leaf Abnormality

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    Plant Disease Symptoms

    Wilt

    Vascular system affected

    Tomato Rhododendron

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    Plant Disease SymptomsRots

    Internally affecting plants

    May be wet or dry rot

    Examples: Fruits, Vegetables,

    Trees

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    PLANT DISEASE SYMPTOMSRoot Rot

    Affects the fine feeder rootsDisease agent enters the crown

    With above ground symptoms

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    Plant Disease Symptoms

    BlightsGeneral death of a plant part or plant

    Fire blight Late blight

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    PLANT DISEASE SYMPTOMS

    Leaf Spots or Blotches

    Dogwood Tomato Dogwood

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    PLANT DISEASE SYMPTOMS

    Cankers

    Sunken areas in wood

    Fungal structures associatedDeath of plant parts

    Rose Spruce

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    PLANT DISEASE SYMPTOMS

    Growth or Galls

    Cell enlargement and division

    Bacteria, Fungi, Virus, Nematodes

    Euonymous Forsythia Tomato

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    PLANT DISEASE SYMPTOMS

    Leaf Abnormality

    Oak Rose

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    A DISEASE SIGN

    Structures produced by the causalagent of that disease that are more

    specific than symptoms and are

    more useful in the accuratediagnosis of a disease

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    PLANT DISEASE MANAGEMENT

    The incitant or pathogen alone

    does not

    bring about the disease.

    Four factors are needed.

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    FOUR FACTORS NEEDED

    FOR A DISEASE TO OCCUR Host or susceptible plant

    Environment Pathogen or disease causing agent

    Time for the disease to occur

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    Plant Disease Management

    Based on the Disease TriangleSeed selection

    Plant selection/resistance

    Planting/fertilization/weed careSanitation (removal,pruning, clean-up)

    Rotation

    Pesticides