Dr. Mary Burrows, Extension Plant Pathology Specialist, Montana State University

 

Contents

  1. Damping off (Pythium, Fusarium, Rhizoctonia and other fungi)
  2. Root rot (Pythium, Fusarium, other fungi)
  3. Rhizoctonia root rot (bare patch) (Rhizoctonia solani)
  4. Dry seed decay (Penicillum, Aspergillus and other fungi)
  5. Cephalosporium stripe (Cephalosporium tritici) of winter wheat
  6. Sharp eyespot (Rhizoctonia cerealis)
  7. Eyespot/strawbreaker foot rot (Pseudocercosporella herpotrichoides)
  8. Fusarium crown rot (Fusarium spp.)
  9. Take-all (Gaeumannomyces graminis var. tritici)
  10. Snow mold (Typhula, Microdochium)
  11. Common root rot (Cochliobolus sativus)
  12. Acknowledgments

 

Damping off (Pythium, Fusarium, Rhizoctonia and other fungi)

photo of a crop with small plants
  • Symptoms
    • Small, yellow plants
    • Reduced emergence
    • Plants emerge then die
  • Risk Factors
    • Continuous crop production
    • Cool soil temperatures
    • Moist soil
    • Lack of seed treatment
  • Management
    • Fungicide seed treatment
      • Use a mix of chemistries to target both oomycetes such as Pythium (metalaxyl or mefanoxam) and fungi such as Fusarium and Rhizoctonia

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Root rot (Pythium, Fusarium, other fungi)

Microscopic image of Pythium
  • Symptoms
    • Small, yellow plants
    • Smaller root mass than healthy plants
    • Brown roots
    • Outer root cortex easily peels off, leaving the inner stele (vascular system) of the root
  • Risk Factors
    • Continuous crop production
    • Cool soil temperatures
    • Moist soil and continued cool temperatures during early crop growth
    • Lack of seed treatment at planting
  • Management
    • Seed treatments are effective for 2-3 weeks after planting.

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Rhizoctonia root rot (bare patch) (Rhizoctonia solani)

close-up photo of a root
  • Symptoms
    • Similar to damping off and dry seed decay
    • Spear-tipping of roots when they are washed (tapered, dark brown or black root tips)
  • Risk Factors
    • Continuous cereal crop production
    • Spraying glyphosate on volunteer and grassy weeds and planting seed within a few days
  • Management
    • Variety selection
    • Soil pH modification with potash is limited in effectiveness

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Dry seed decay (Penicillum, Aspergillus and other fungi)

photo of decaying seeds
  • Symptoms
    • Seeds may decay in the soil or seedlings may become blighted and killed below the soil surface
    • Stands are thin and uneven or lacking plants in small to large areas
    • Seeds may be covered with green or white fungal mycelia, soil may stick to seeds
  • Risk Factors
    • Planting into dry soil with no moisture for 2-3 weeks after planting
    • Lack of seed treatment
  • Management
    • Fungicide seed treatment

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Cephalosporium stripe (Cephalosporium tritici) of winter wheat

photo of a wheat plant with a yellow stripe up the leaf
  • Symptoms
    • Dwarfed plants with one or two continuous yellow stripes on the leaf
    • Nodes on stem may be darkened
    • White heads at maturity
  • Risk factors
    • Continuous winter wheat cropping
    • Freeze-thaw cycles which allow the fungus to enter the roots
    • Early seeding
  • Management
    • Variety selection
    • Crop rotation
    • Delayed planting
    • Tillage

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Sharp eyespot (Rhizoctonia cerealis)

photo of lesions on a plant stem
  • Symptoms
    • Lesions on crown elongated eye-shape
    • Dark halo surrounding tan center
    • White heads at maturity
    • Lodging; infects through leaf sheath, lesions often start on external leaf sheath and expand into center of stem
    • Girdling plant
  • Risk factors
    • Continuous cereals
    • No-till with crop residue
    • Moist, cool weather
  • Management
    • Crop rotation
    • Variety selection
    • Irrigation management to reduce humidity in the canopy
    • Light tillage to reduce residue
    • Fungicide application

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Eyespot/strawbreaker foot rot (Pseudocercosporella herpotrichoides)

another close-up photo of lesions on stems
  • Symptoms
    • Lesions on crown elongated eye-shape
    • Dark halo surrounding brown center
    • White heads at maturity
    • Lodging; infects through leaf sheath, lesions often start on external leaf sheath and expand into center of stem
    • Girdling plant
  • Risk factors
    • Continuous cereals
    • No-till with crop residue
    • Moist, cool weather
  • Management
    • Crop rotation
    • Variety selection
    • Irrigation management to reduce humidity in the canopy
    • Light tillage to reduce residue
    • Fungicide application

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Fusarium crown rot (Fusarium spp.)

close-up photo of a root system that is showing a brown discoloration
  • Symptoms
    • Brown discoloration of subcrown internode and first two nodes of the crown
    • White heads at maturity
  • Risk factors
    • Continuous wheat production
    • No-till with wheat crop residue
    • High nitrogen
    • Soil moisture fluctuations
  • Management
    • Crop rotation
    • Variety selection
    • Proper fertilization
    • Irrigation management to maintain continuous moisture
    • Light tillage to reduce residue where applicable

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Take-all (Gaeumannomyces graminis var. tritici)

close-up photo of a root system that's showing a black discoloration
  • Symptoms
    • Solid or streaked obsidian-black discoloration of first one or two nodes of the crown
    • Black discoloration of subcrown internode
    • White heads at maturity
  • Risk factors
    • Continuous wheat production (although after many years of continuous wheat there may be take all decline, a reduction in disease)
    • No- till with wheat crop residue
    • High soil pH
    • Nutritional stress
  • Management
    • Crop rotation
    • Variety selection
    • Proper fertilization
    • Grassy weeds control
    • Light tillage to reduce residue where applicable

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Snow mold (Typhula, Microdochium)

photo of a young plant that is displaying symptoms of snow mold
  • Symptoms
    • Speckled snow mold (Typhula)
      • Leaves are bleached white/ tan, small dark fungal structures (sclerotia) scattered
    • Pink snow mold (Microdochium)
      • Pink fungal structures (mycelium, conidia) on yellow or dying leaves
  • Risk factors
    • Prolonged deep snow
  • Management
    • Crop rotation
    • Early seeding to develop larger, more tolerant plants

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Common root rot (Cochliobolus sativus)

photo of a root system that is displaying signs of common root rot
  • Symptoms
    • Brown to black, often streaky discoloration of first one or two nodes of the crown
    • Dark brown spots on subcrown internode
    • White heads at maturity
  • Risk factors
    • Continuous wheat production
    • No-till with wheat crop residue
    • High nitrogen
    • Soil moisture fluctuations
  • Management
    • Crop rotation
    • Variety selection
    • Proper fertilization
    • Irrigation management to maintain continuous moisture
    • Light tillage to reduce residue where applicable

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Acknowledgments

Photos courtesy of MSU Plant Pathology Department slide collection; Jeff Johnston, Plant Sciences and Plant Pathology, MSU; Larry Osborne, South Dakota State University; Tim Murray, Washington State University; CIMMYT; and HGCA; Wikimedia Commons.

Original July 2009 PDF (3MB)

 

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