Guide to Common Foliar Diseases of Cereal Crops in Montana

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

Contents

1. Tan spot (Pyrenophora tritici-repentis) of wheat
2. Septoria leaf spot (Septoria tritici and Stagnospora nodorum) of wheat and barley
3. Physiological leaf spot (abiotic disorder) of wheat and barley
4. Bacterial leaf blight and black chaff (Xanthomonas translucens pv. translucens and X. campestris pv. vesicatoria) of wheat and barley
5. Net blotch and spot blotch (Pyrenophora teres) and spot blotch (Bipolaris sorokiniana) of barley
6. Scald (Rhynchosporium secalis) of barley
7. Stripe rust (Puccinia striiformis) of wheat and barley
8. Leaf rust of wheat (Puccinia triticina) and barley (Puccinia hordei)
9. Stem rust of wheat and barley (Puccinia graminis f. sp. tritici)
10. Acknowledgments

Tan spot (Pyrenophora tritici-repentis) of wheat

• Symptoms
  • Small, yellow spots on the leaves when the fungus first infects the leaf which expand into an eye shape, sometimes with a brown (necrotic) pupil and a yellow halo, if there is enough moisture
  • Yellow halo much broader than seen with Septoria
  • Straw will have tiny black, raised structures (pseudothecia)
  • Seed can have red smudge
• Risk Factors
  • Continuous wheat production
  • No-till with wheat residue
  • Irrigation
  • Infection requires 6-24 hours of moisture and moderate temperatures (68-82°F)
• Management
  • Crop rotation
  • Residue reduction
  • Use of best-yielding variety in your region
  • Protect flag leaf area with fungicides

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Septoria leaf spot (Septoria tritici and Stagnospora nodorum) of wheat and barley

• Symptoms
  • Small, yellow spots on the leaves when the fungus first infects the leaf, which expand into tan to brown and irregular to lens-shaped lesions with little to no yellow halo
  • If very moist small black specks (pycnidia) will be formed in the lesion
• Risk Factors
  • Continuous cereal production
  • No-till with cereal residue
  • Irrigation
  • Infection requires 6-24 hours of moisture and moderate temperatures (68-82°F)
• Management
  • Crop rotation
  • Residue reduction
  • Use of best-yielding variety in your region
  • Protect flag leaf area with fungicides

contents

Physiological leaf spot (abiotic disorder) of wheat and barley

• Symptoms
  • Can be confused with tan spot and Septoria leaf spot but symptoms are uniform on leaf and symptoms on all leaves, not just lower leaves
  • Edges of lesions are distinct, not diffuse
• Risk Factors
  • High pH soil
  • Variety susceptibility
• Management
  • Variety selection
  • Soil pH modification with potash is limited in effectiveness

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Bacterial leaf blight and black chaff (Xanthomonas translucens pv. translucens and X. campestris pv. vesicatoria) of wheat and barley

• Symptoms
  • Small, water-soaked spots on leaves which elongate into linear streaks that become necrotic tan or brown
  • Often the tips of the leaves become shredded
  • Leaves feel ‘shellaced’ or slick; when very wet bacteria ooze from leaves or glumes
• Risk Factors
  • Saving seed from a crop infested with bacterial blight or black chaff
• Management
  • Variety selection
  • Use clean seed

contents

Net blotch and spot blotch (Pyrenophora teres) and spot blotch (Bipolaris sorokiniana) of barley

• Symptoms
  • Small, round to oblong brown spots or netlike necrosis
  • Net blotch can occur in a spot form
• Risk Factors
  • Continuous barley
  • No-till with barley residue
  • Irrigation
• Management
  • Crop rotation
  • Variety selection
  • Irrigation management to reduction of humidity in the canopy
  • Light tillage to reduce residue
  • Fungicide application

contents

Scald (Rhynchosporium secalis) of barley

• Symptoms
  • Very distinct dark brown ring around a tan center
• Risk Factors
  • Continuous barley
  • No-till with barley residue
  • Irrigation
• Management
  • Crop rotation
  • Variety selection
  • Irrigation management to reduction of humidity in the canopy
  • Light tillage to reduce residue
  • Fungicide application

contents

Stripe rust (Puccinia striiformis) of wheat and barley

• Symptoms
  • Yellow pustules occurring in stripes
  • Different subspecies infect wheat and barley
  • Spores are wind-dispersed
  • Overwinters on wheat and other grasses
• Risk Factors
  • Overwintering stripe rust
  • Incidence of stripe rust in other wheat-growing regions in North America
• Management
  • Variety selection
  • Fungicides

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Leaf rust of wheat (Puccinia triticina) and barley (Puccinia hordei)

• Symptoms
  • Small, red-orange spore masses (pustules) on leaves
  • Spores rub off on your finger
  • Older pustules or those on resistant varieties will appear black
  • Spores are wind-dispersed
• Risk Factors
  • Incidence of leaf rust in other cereal-growing regions in North America (particularly south and east of Montana)
  • Wind conditions and time of infection
  • Infection is favored by 6-8 hours of dew and temperatures from 60 to 80°F
• Management
  • Variety selection
  • Fungicides

contents

Stem rust of wheat and barley (Puccinia graminis f. sp. tritici)

• Symptoms
  • Small, red-brown spore masses (pustules) with frayed edges on stems and leaves
  • Spores rub off on your finger
  • Older pustules or those on resistant varieties will appear black
  • Spores are wind-dispersed
• Risk Factors
  • Incidence of stem rust in other cereal-growing regions in North America (particularly south and east of Montana)
  • Wind conditions and time of infection
  • Infection is favored warm day temperatures from 77 to 86°F and cool night temperatures 59 to 68°F and dew
  • Barberry is the alternate host
• Management
  • Variety selection
  • Fungicides

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Acknowledgments

Photos courtesy of the MSU Pathology Department slide collection; Rick Engel, Land Resources & Environmental Sciences, MSU; North Dakota State University.

Original July 2009 PDF (2.4MB)

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