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Potato Diseases

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Potato Diseases. Fungal. Actinomycete. Common Scab - Streptomyces scabies ... Pathogen: Streptomyces scabies. Most common on soils with pH 5.5-7.5 ... – PowerPoint PPT presentation

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Title: Potato Diseases


1
Potato Diseases
  • Early Blight - Alternaria solani
  • Late Blight - Phytophthora infestans
  • Rhizoctonia Canker - Rhizoctonia solani
  • Silver Scurf - Helminthosporium solani
  • Verticillium Wilt - Verticillium albo-atrum and
    V. dahliae
  • Common Scab - Streptomyces scabies
  • Bacterial Black Leg and Soft Rot - Erwinia
    carotovora pvar. carotovora and pvar. atroseptica
  • Bacterial Ring Rot - Clavibacter michiganensis
    subsp. sepedonicus

2
Potato Early Blight
3
Early Blight
4
Alternaria solani
5
Early Blight
6
Potato Early Blight
7
Potato Early Blight Tuber Symptoms
8
Hygrothermograph
9
Potato Diseases - Early BlightKey Points
  • Pathogen Alternaria solani
  • Symptoms
  • Leaf lesions frequently have "bulls-eye" or
    "target spot" appearance
  • Advanced lesions usually have angular margins
    because they are limited by leaf veins
  • As infection progresses, entire leaf becomes
    chlorotic, then dies
  • The fungus persists in the soil, infected debris,
    and tubers
  • The disease is more severe when potato plants are
    under stress, have been injured or have poor
    nutrition

10
Potato Diseases - Early Blight Control Strategies
  • Protectant fungicides
  • apply according to blight forecasting systems for
    maximum efficacy
  • Allow tubers to mature in ground before digging
  • wait at least 7 days after vine kill before
    harvest.
  • Avoid injury of tubers during harvest

11
Late Blight
12
Late Blight
13
Late Blight
14
Late Blight
15
Late Blight
16
Late Blight
17
Life cycle of Phytophthora infestans
Agrios, G., 2nd Edition
18
Potato Diseases - Late Blight Key Points
  • Pathogen Phytophthora infestans
  • Symptoms
  • leaf lesions initially small, water-soaked
  • expand rapidly to large brown to purplish-black
    lesions killing entire leaflets and spreading
    through petiole to stem, eventually killing
    entire plant
  • under moist conditions white velvety area of
    sporangia and sporangiophores visible around edge
    of lesions (mainly on underside of leaf)
  • Disease progresses very quickly under optimum
    conditions.
  • Fungus overwinters in infected tubers (cull piles
    or infected seed tubers)
  • Also infects tomato and other solanaceous crops
    and weeds such as hairy nightshade

19
Potato Diseases - Late BlightControl Strategies
  • Eliminate cull piles
  • Control weed hosts
  • Eliminate volunteer potatoes
  • Plant disease-free seed
  • Treat crop with currently registered fungicides
  • Combine with disease forecasting
  • Soil coverage by means of adequate hilling can
    reduce infection of tubers
  • Kill vines two weeks before harvest so sporangia
    on infected plant tissue die
  • Check and remove infected tubers at harvest
  • Monitor stored potatoes for decay

20
Rhizoctonia Canker
21
Rhizoctonia Canker
22
Potato Diseases - Rhizoctonia CankerKey Points
  • Pathogen Rhizoctonia solani
  • Symptoms
  • plants most severely damaged in spring just after
    planting
  • stem lesions are reddish-brown, may girdle stem
    leading to
  • death of shoot (before or after emergence)
  • stunting of plant
  • aerial tubers
  • leafroll symptoms
  • discoloration of foliage, chlorosis
  • tuber symptoms black or dark brown sclerotia on
    surface
  • Can overwinter as sclerotia on tubers or in the
    soil, or as mycelium on plant debris.
  • Low soil temperatures and high soil moisture
    favor infection

23
Potato Diseases - Rhizoctonia CankerControl
Strategies
  • Crop rotation
  • Use disease free seed pieces
  • Plant on well drained soil
  • Deep planting increases risk of stem infection

24
Silver Scurf
25
Silver Scurf
26
Potato Diseases - Silver ScurfKey Points
  • Pathogen Helminthosporium solani
  • Symptoms
  • light brown, circular spots with indistinct
    borders may enlarge to cover considerable area of
    tuber
  • affected areas have distinct silvery sheen
  • tubers more likely to shrivel in storage
  • Disease found world wide wherever potatoes are
    grown.
  • Transmission is primarily from infected seed
    pieces
  • The disease continues in storage as long as
    conditions are favorable

27
Potato Diseases - Silver ScurfControl Strategies
  • Use disease free seed
  • Treat with with currently registered fungicides
  • Harvest tubers as soon as they are mature
  • Avoid free moisture on tubers

28
Verticillium Wilt
29
Verticillium Wilt
30
Potato Diseases - Verticillium WiltKey Points
  • Pathogens Verticillium albo-atrum and V.
    dahliae
  • Symptoms
  • early senescence of plants - leaves become
    yellow, die
  • single stems or one side of stem often affected
    first
  • brown vascular discoloration
  • Soil fungi that infect many species and can
    survive in the soil in the form of microsclerotia
  • Wilting first occurs on hot dry days
  • Inoculum can be distributed by movement of
    contaminated soil which adheres to seed tubers or
    equipment
  • Incidence of Verticillium Wilt is increased with
    the presence of parasitic nematodes

31
Potato Diseases - Verticillium WiltControl
Strategies
  • Rotate with non-host crops such as cereals,
    grasses and legumes
  • Control weed hosts
  • Treat soil with a currently available fumigant if
    pathogen population is above economic threshold
  • Avoid over irrigation during period of emergence
    to tuberization

32
Common Scab
33
Common Scab of Potato Streptomyces scabies
34
Common Scab
35
Potato Diseases - Common ScabKey Points
  • Pathogen Streptomyces scabies
  • Most common on soils with pH 5.5-7.5
  • Warm, dry soils and early season stress favor
    infection and lesion development
  • Soil borne and tuber borne
  • May be introduced on seed potatoes
  • Limited host range - carrot, beet, parsnips,
    radishes, rutabagas, spinach, sugar beets,
    turnips
  • Tubers susceptible as soon as they form
  • Infection through lenticels
  • Once periderm forms, tubers no longer susceptible
  • Survives digestive tract of animals, distributed
    in manure

36
Potato Diseases - Common ScabControl Strategies
  • Manure applied to soil may favor scab infection
  • Consider 3-5 year rotations - alfalfa, corn,
    peas, rye, snap beans, soybeans
  • Adjust soil pH to 5.2-5.8
  • Avoid moisture stress especially at tuber
    initiation and early tuber growth
  • Some cultivars with high tolerance e.g. Frontier
    Russet, RedDale, Russet Burbank, Superior
  • Treatment of seed with mancozeb fungicide dust
    reduces scab
  • In-furrow application of Mocap granular
    insecticide reduces scab

37
Bacterial Black Leg Soft Rot
38
Black Leg
39
Bacterial Soft Rot
40
Potato Diseases - Bacterial Black Leg and Soft
Rot - Key Points
  • Pathogens Erwinia carotovora pvar. carotovora
    and pvar. atroseptica
  • Symptoms
  • Soft rot wet, slimy cream to tan colored decay,
    with distinct margins. May become brown to
    black, foul smelling with ropy consistency with
    invasion of secondary organisms
  • Black leg black, wet looking decay of stem,
    moving from seedpiece up stem. Plants commonly
    stunted, wilted
  • Bacteria overwinter on or in tubers in storage
  • Primary inoculum is in the tuber seed piece
  • Bacteria enter lenticels, wounds or growth cracks
  • Bacteria can move in soil water
  • Tubers can become infected in storage if inoculum
    runs onto clean potatoes and enters through
    lenticels or wounds

41
Potato Diseases - Bacterial Black Legand Soft
Rot - Control Strategies
  • Plant in well drained soil
  • Do not over irrigate
  • Cut tuber seed pieces 3-5 days before planting,
    keep at 55-60 F and 90 RH to allow cut surfaces
    to suberize before planting.
  • Disinfest seed piece cutting tools
  • Harvest tubers only when mature and when soil
    temperatures are less than 68 F
  • Do not wash tubers before storage
  • Keep storage temperatures from 34 to 40 F in a
    well ventilated area

42
Bacterial Ring Rot
43
Bacterial Ring Rot
44
Potato Diseases - Bacterial Ring RotKey Points
  • The pathogen - a bacterium, Clavibacter
    michiganensis subsp. sepedonicus (formerly
    Corynebacterium sepedonicum)
  • Symptoms
  • wilting of leaves and stems after midseason
  • often affects only one or two stems of a plant
  • lower leaves, slightly rolled at the margins and
    pale green usually first to wilt
  • milky white exudate can be squeezed from vascular
    system of tubers
  • Symptom expression is most common following warm
    dry weather
  • Overwinters in tubers either in storage or left
    behind in the soil
  • Contaminated knives or picking equipment can
    disseminate the inoculum
  • Infection occurs through wounds of any plant part

45
Potato Diseases - Bacterial Ring RotControl
Strategies
  • Use certified, disease free seed and follow
    careful sanitation procedures
  • Dispose of all tubers if the disease is found in
    the crop
  • Disinfest all equipment used for growing and
    harvesting the crop
  • Use clean new bags for each new years crop
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