Plant Disease - PDF by pcherukumalla

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									  PLANT DISEASE
             Or
     Plants Do Get Sick


     John F. Baniecki, Ph.D.
Extension Specialist and Professor
     West Virginia University
WHAT IS A PLANT DISEASE?
 A plant disease may be defined as
 any disturbance that prevents the
 normal development of a plant and
 reduces its economic or aesthetic
 value.
ASSOCIATED WITH A DISEASE ARE:


            SYMPTOMS

              SIGNS
              A
           SYMPTOM
The visible response of a plant to a
causal agent over time.

May be caused by:
    living agents (Biotic)
    non-living agents (Abiotic)
PLANT DISEASE SYMPTOMS

 Produced by non-living agents
 (Abiotic)
      Environmental
      Chemical
      Nutritional
      Cultural
PLANT DISEASE SYMPTOMS

 Environmental
    Cold
    Heat or Drought
    Lightning
    Wetness
PLANT DISEASE SYMPTOMS
        Environmental
     Cold------------Brrrrrrrrrr!
PLANT DISEASE SYMPTOMS
       Environmental
    Heat    or    Drought
PLANT DISEASE SYMPTOMS
      Environmental
      Lightning Damage
PLANT DISEASE SYMPTOMS
       Environmental
  Wetness   Results:   Root Rot
PLANT DISEASE SYMPTOMS
         Chemical

  Salt   Fertilizer   Pesticide
PLANT DISEASE SYMPTOMS

        Nutritional
PLANT DISEASE SYMPTOMS
        Cultural
       Tree Girdling
PLANT DISEASE SYMPTOMS

        Cultural
        Overwatering
PLANT DISEASE SYMPTOMS

 Produced by Living Agents (Biotic)
    Fungi
    Bacteria
    Viruses, Viroids, Mycoplasmas
            Spiroplasms
    Nematodes
    Parasitic Vascular Plants
PLANT DISEASE SYMPTOMS

 Fungi
  Lower forms of plant life
  Microscopic thread-like growth
  Lack chlorophyll
  Attack higher forms of plant life
  Spread by wind, rain, insects
PLANT DISEASE SYMPTOMS

 Fungi
PLANT DISEASE SYMPTOMS
 Fungi cause:
   Leaf spots or Blotches
   Blight
   Cankers
   Root rot
    Wilt and/or reduced growth, death
   Trunk rot
   Abnormal growth or galls
PLANT DISEASE SYMPTOMS

 Bacteria
  Single celled organisms
  Enter the plant through natural
     openings or plant injuries
  Spread by wind, rain, insects
PLANT DISEASE SYMPTOMS
 Bacteria   Streaming from a plant
PLANT DISEASE SYMPTOMS
 Bacteria cause:
   Leaf spots or Blotches
   Blight
   Cankers
   Root rot
   Wilt and/or reduced growth, death
   Abnormal growth or galls
PLANT DISEASE SYMPTOMS
 Viruses
  Submicroscopic, replicate inside
     living cells
 Composed of a piece of genetic
    material (either RNA or DNA)
    surrounded by a protein coat
 Takes over the plant cell metabolism
PLANT DISEASE SYMPTOMS
 Viruses
 Gain entry to cells through a wound or
   during insect feeding
 Spread by man and insects
 Occurs in weeds and “other” plants
PLANT DISEASE SYMPTOMS
 Viruses
 Can be maintained in a population of
  plants   or
 transferred from plant to plant by:
    vegetative propagation
     grafting
PLANT DISEASE SYMPTOMS
 Viruses
 Can also be maintained or transferred by:
   dodder, a parasitic plant
   mechanically in sap on hands, tools,
   ropes, etc.
PLANT DISEASE SYMPTOMS
 Viruses
  Can also be maintained or transferred
  by:
    feeding by nematodes, mites, aphids,
    leaf hoppers, thrips, and whiteflies
PLANT DISEASE SYMPTOMS
 Viruses
   Can also be maintained:
       on or inside seeds
       in pollen
       in certain root-infecting fungi
PLANT DISEASE SYMPTOMS
 Viruses   Tobacco Mosaic Virus
PLANT DISEASE SYMPTOMS

 Viruses cause:
     Dead areas on leaves
      Abnormal growth
      Reduced growth, death
PLANT DISEASE SYMPTOMS
 Viroids
     Piece of genetic material
      Has no protein coat
      Divert plant metabolism to
         produce more viroids
      Spread by vegetative
         propagation
PLANT DISEASE SYMPTOMS
 Potato spindle tuber viroid
    Short, upright, stunted growth
PLANT DISEASE SYMPTOMS
 Mycoplasmas, Spiroplasms, and
  Phytoplasms
     Similar to bacteria
     Have no cell wall
     Found in the infected plant water-
         and food- conducting vessels
     Leaf hoppers transmit mycoplasmas
PLANT DISEASE SYMPTOMS
 Mycoplasmas, Spiroplasms, and
 Phytoplasms
   cause:
    Growth abnormalities
    Yellowing
     Short internodes
     Distortion of leaf and flower tissue
PLANT DISEASE SYMPTOMS
 Stubborn disease of citrus
      Spiroplasma
 Uneven fruit size, reduction
PLANT DISEASE SYMPTOMS
 Carrot aster yellows phytoplasm
   Yellowing of foliage, hairy roots
    and internal root necrosis
PLANT DISEASE SYMPTOMS

 Nematodes
   Microscopic worms
   Found in the soil
   Occurs in weeds and “other” plants
   Spread by man
PLANT DISEASE SYMPTOMS
 Nematodes
PLANT DISEASE SYMPTOMS

 Nematodes cause:
  Abnormal growth or galls
  Reduced growth, death
PLANT DISEASE SYMPTOMS
 Parasitic vascular plants
    Dodder, mistletoe, witchweed,
    Indian pipes, beech drops


 Gain nutrients by parasitizing seed-
   bearing plants
PLANT DISEASE SYMPTOMS
 Parasitic vascular plants
    Dodder
PLANT DISEASE SYMPTOMS
 Parasitic vascular plants
    Mistletoe
PLANT DISEASE SYMPTOMS
 Parasitic vascular plants
    Witchweed
PLANT DISEASE SYMPTOMS
 Parasitic vascular plants
    Indian pipes
PLANT DISEASE SYMPTOMS
 Parasitic vascular plants
    Beech drops
PLANT DISEASE SYMPTOMS
  • Wilts
  • Rots
  • Root Rot
  • Blights
  • Leaf Spots or Blotches
  • Cankers
  • Growth or Galls
  • Leaf Abnormality
Plant Disease Symptoms
 Wilt
   Vascular system affected
   Tomato           Rhododendron
Plant Disease Symptoms
                Rots
     Internally affecting plants
       May be wet or dry rot
   Examples: Fruits, Vegetables,
                Trees
PLANT DISEASE SYMPTOMS
              Root Rot
    Affects the fine feeder roots
  Disease agent enters the crown
  With above ground symptoms
Plant Disease Symptoms
 Blights
   General death of a plant part or plant

  Fire blight            Late blight
 PLANT DISEASE SYMPTOMS
      Leaf Spots or Blotches

Dogwood     Tomato        Dogwood
PLANT DISEASE SYMPTOMS
            Cankers
     Sunken areas in wood
  Fungal structures associated
      Death of plant parts
     Rose              Spruce
PLANT DISEASE SYMPTOMS
          Growth or Galls
     Cell enlargement and division
   Bacteria, Fungi, Virus, Nematodes

 Euonymous   Forsythia       Tomato
PLANT DISEASE SYMPTOMS
      Leaf Abnormality
    Oak             Rose
A DISEASE SIGN
Structures produced by the causal
agent of that disease that are more
specific than symptoms and are
more useful in the accurate
diagnosis of a disease
PLANT DISEASE MANAGEMENT

  The incitant or pathogen alone
             does not
    bring about the disease.
    Four factors are needed.
FOUR FACTORS NEEDED
FOR A DISEASE TO OCCUR
  Host or susceptible plant
  Environment
  Pathogen or disease causing agent
  Time for the disease to occur
Plant Disease Management

 Based on the Disease Triangle
   Seed selection
   Plant selection/resistance
   Planting/fertilization/weed care
   Sanitation (removal,pruning, clean-up)
   Rotation
   Pesticides

								
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