Diseases of Snap Bean

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Diseases of Snap Bean

• White Mold - Sclerotinia sclerotiorum
• Root Rot - Fusarium, Aphanomyces, Pythium spp.
• Powdery Mildew - Erysiphe polygoni

• Bacterial Brown Spot - Pseudomonas syringae pv.
  syringae
• Common Blight - Xanthomonas campestris pv.
  phaseoli
• Halo Blight - Pseudomonas syringae pv.
  phaseolicola

• Hail Injury
• 2,4-D Injury

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Bacterial Bean Problems
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Common Blight
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Bacterial Brown Spot
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Bacterial Brown Spot - Pod
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Bacterial Brown Spot - Pod
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Halo Blight
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Halo Blight
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Bacterial Diseases of Snap BeanKey Points

• Pathogens and symptoms
• bacterial brown spot - Pseudomonas syringae pv.
  syringae - brown lesions of varying size, lack
  halos
• common blight - Xanthomonas campestris pv.
  phaseoli - lesions become large, dry, dark brown,
  coalesce
• halo blight - Pseudomonas syringae pv.
  phaseolicola - small brown lesions, surrounded by
  large chlorotic halo
• Survival and transmission
• all three may be carried via the seed
• pathogens enter host plants through both wounds,
  natural openings
• inoculum disseminated by wind driven rain and
  irrigation
• pathogens survive on a number of leguminous hosts

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Bacterial Diseases of Snap BeanControl Strategies

• Eliminate weeds and volunteer bean hosts
• Use pathogen-free seed or resistant varieties
• Use a two-year rotation with a non-host crop
• For commercial production use currently
  registered chemical controls

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White Mold
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White Mold
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White Mold
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White Mold
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White Mold
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White Mold
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White Mold
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White Mold
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Birds Nest Fungus
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Snap Bean Diseases - White MoldKey Points

• Pathogen Sclerotinia sclerotiorum
• infects over 360 species of plants
• Symptoms and signs
• lesions on leaves, stems and pods - initially
  water-soaked, drying to papery tan appearance
• lesions girdling stems result in death of stem or
  entire plant
• white cottony mycelium and black sclerotia often
  associated with lesions
• Sclerotia produced by the fungus survive in soil
  up to five years or longer
• Dense canopy of plant tissue that creates cool
  moist microclimate favors plant infection
• Senescent flowers are most common site of initial
  infection

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Snap Bean Diseases - White Mold Control
Strategies

• Varieties with more upright, open structure less
  likely to be infected
• Plant crop to promote rapid drying of tissue
  after wetting
• Plant rows parallel to prevailing winds
• Wide row spacing
• Rotation with non-host crops such as corn and
  small grains
• Use currently registered fungicides during the
  flowering period

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Common Root Rot
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Common Root Rot
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Common Root Rot
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Snap Bean Diseases - Bean Root RotKey Points

• Pathogen Complex of fungi
• May involve Fusarium, Aphanomyces, Pythium
  species
• soil inhabiting pathogens which can attack bean
  roots at any time during the growing season
• Symptoms
• stunting and wilting of plant
• discoloration and death of roots and lower
  portion of stem
• lower portion of stem may become mushy
• Generlly most severe in moist soil but
  temperature requirements differ for the different
  pathogens
• Pathogen resting structures allow long-term
  survival
• Root exudates from host stimulate fungal growth
  and infection
• Severity can increase if more than one fungus
  present

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Snap Bean Diseases - Bean Root RotControl
Strategies

• Have soil tested for root rot potential before
  deciding which fields will be planted to beans
• Minimize soil compaction
• Plant in well-drained, light soil. In the home
  garden, raised beds may help with control
• Chemical seed treatment is effective for Pythium
  root rot, but not for rot caused by Fusarium or
  Aphanomyces

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Powdery Mildew
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Hail Injury
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2,4-D Injury