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Basic Plant Pathology

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Basic Plant Pathology Jennifer Davidson * With proper training, nematodes can be easily identified once they have been extracted from soil or infected plant material. – PowerPoint PPT presentation

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Title: Basic Plant Pathology


1
Basic Plant Pathology
  • Jennifer Davidson

2
Learning Objectives
  • Define plant pathology
  • Economic importance of plant diseases
  • Pathogenic and Non-pathenogenic diseases
  • Disease triangle
  • Fungal diseases, fungi reproduction and fungal
    infection
  • Viruses and how viruses are spread
  • How diseases are caused by nematodes

3
Disease Triangle
Host
Pathogen
Disease
Environment
4
2
1
4
3
5
Fungi
  • Rust
  • Leaf spot
  • Wilt
  • canker

6
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7
Hyphae
Mycelia
8
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9
Cleistothecium-powdery mildew
10
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11
Thielaviopsis
12
Oospore- Pythium
13
bacteria
  • Scorch
  • Wilt
  • fireblight

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15
High magnification 400X
Very High magnification Electron microscopy
16
Virus
  • Tobacco -Mosaic

17
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18
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19
Nematodes
  • Root knot

20
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21
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22
BREAK
23
Plant Problems Not Caused by Disease
  • Cultural
  • Environmental

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29
Cultural Disease Controls
  • Avoiding the pathogen
  • Buy seed from a reputable source
  • Inspect plants prior to purchase
  • Control alternate hosts

30
Cultural Disease Control
  • Avoiding conducive environmental conditions
  • Moderate soil moisture
  • Reduce humidity
  • Fertilize plants properly
  • Be aware of activities surrounding your plants

31
Cultural Disease Controls
  • Sanitation
  • Disinfest tools
  • Remove diseases plants promptly
  • Remove senescent plant parts promptly

32
Chemical Disease Control
  • Fungicides, bactericides, nematicides
  • Protectants
  • Systemics
  • Fumigants

33
Resistant Plants
  • ASK QUESTIONS!!!!
  • Which disease?
  • Are diseases in your area?
  • Has it been tested?
  • PLANTS MAY LOSERESISTANCE

Nearly Wild Roses
34
Common Plant Diseases in the Landscape
35
Seridium Canker
  • This disease is particularly prevalent on drought
    stressed Leyland Cypress trees during hot
    weather.
  • Fungus Seiridium unicorne.
  • Symptoms Yellowing and browning of old foliage
    precedes fading and death of twigs and branches.
    Sunken, long cankers with a reddish tinge develop
    at wounds on bark, bark is darkened and resin
    exudes from margins of cankers. Infection can
    occur on any part of the plant and stage of the
    tree. Infected trees look thinly branched.

36
Leaf Rusts
  • Leaf rust diseases are common on roses,
    snapdragons, hollyhocks, crabapple, and most
    recently, daylilies. The most diagnostic sign of
    the disease are the raised pustules that rupture
    to release powdery, orange to rust-colored spores
    on the underside of the affected leaf.

37
Rhizoctonia Root Rot
  • They occur in wet soils with limited soil
    drainage (porosity) or in areas that are
    over-watered or remain wet due to location of
    gutters and downspouts, air conditioning units
    and slopes, etc. All landscape plants (trees,
    shrubs and flowers) are susceptible to root rot.

Damping Off
38
Pythium Root Rot
  • Plants attacked by soil-borne pathogens may be
    stunted, develop lesions at the soil line, or
    wilt and collapse. When larger plants become
    infected with root rot pathogens, aboveground
    symptoms include poor growth, off-color foliage,
    yellowing and dropping of lower leaves, wilting
    and death. Infected roots are usually brown, soft
    and decayed. Some root rot pathogens invade the
    lower stem as well, causing tan, dry cankers or a
    soft, dark-brown, watery stem rot

Brown, necrotic roots
39
Powdery Mildew
  • Powdery mildew is characterized by the presence
    of whitish fungal growth on the surfaces of
    leaves, stems, and flowers. Infection of young,
    expanding leaves or shoots can result in severe
    distortion.
  • Very common on pruned crapemyrtles.

40
Leaf Gall, Exobasidium
  • Common on azalea, rhododendron, mountain laurel
    (Kalmia) and camellia in the spring during wet,
    humid, cool weather. Infection only occurs at
    leaf or flower bud break if favorable
    environmental conditions exist.

41
Fire Blight
  • Fireblight is a destructive, highly infectious
    and widespread disease caused by the bacterium
    Erwinia amylovora. Fireblight affects plants in
    the Rosaceae family such as pear, crabapple,
    cotonoaster, photinia, pyracantha, quince, etc.

42
Botrytis Blight
  • The fungus commonly invades wounded or senescent
    tissue, such as fallen flower petals or other
    fresh plant residues. It can also invade healthy
    tissue in contact with infected residues. Masses
    of fuzzy, grayish-brown spores on thin black
    stalks develop on infected plant tissues under
    cool, moist, humid, cloudy conditions.

43
Sooty Mold
  • Fungus that grows on the secretions of piercing
    sucking insects such as aphids, whitefly.
  • Remove the food sources, the fungus will go away.

44
Bacterial Diseases
  • Leaf spots are initially water-soaked or greasy
    in appearance, often angular, and concentrated
    along leaf veins or margins
  • Requires water to enter leaf
  • Fungus gnat larvae can spread soft rot bacteria

45
Viral Diseases
  • Virus symptoms are often quite striking and
    distinctive. Chlorotic mottling, ringspots and
    line patterns on the foliage or stems may occur.
  • Stunting is commonly observed.
  • Destoy plants, rid area of vectors.

Yellow Ringspot Pattern on Lily
46
Turf Diseases
See pathology reports! 
47
Questions?
What are the two types of plant diseases? What
three factors are required for a pathogenic
disease? How are viruses spread? What are
nematodes and how can they cause plant
disease? How can plant diseases be controlled?
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