Diseases of Oats

 
 
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 Anthracnose | Yellow Dwarf (Red Leaf) | Covered Smut | Loose Smut | Crown Rust | Ergot | Stem Rust | Common Root Rot | Halo Blight | Leaf Blotch | Septoria Leaf Blotch | Oat Blue Dwarf | Brome Mosaic | Take-all | Fusarium Head Blight | Non-Infectious | Other diseases of Oats

Anthracnose
Colletotrichum graminicola

What to look for?
Sometimes shows up in central and western Alberta. Severe infection causes premature ripening and bleaching of plants with increased lodging susceptibility. The fungus survives on crop residue and disease spread is favored by wet weather.

Numerous yellowish streaks on the leaves.
Photo: Tekauz
Picture description
Numerous yellowish streaks on the leaves.
Fungal infection on the node.
Photo: Tekauz
Picture description
Fungal infection on the node.
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Management strategy
Control is by improved fertility and rotation with non-cereal crops.

A more complete description of anthracnose.

Yellow Dwarf (Red Leaf)
Barley Yellow Dwarf Virus

This is an aphid-borne virus that shows up in some years. Many virus strains and aphid species are found in the crop. Late sown oats are more susceptible than early sown due to build-up of the aphid vector. Infection takes up to 2 weeks to show-up often as dull red flag leaves.

What to look for?
Red virus infected leaves.
Photo: Davidson
Picture description
Red virus infected leaves.
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Management strategy
Most new oat cultivars have good resistance to this virus which is helped by early seeding of the crop. Late infections in the maturing crop are usually symptomless but yields may be decreased.
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A more complete description of red leaf in oats.

Covered Smut
Ustilago koller

What to look for?
Both loose and covered smut of oats are very similar in their life cycles. Infection in both takes place from contaminated seed at the seedling stage. The heads of both disease smuts types emerge at the same time as healthy heads but are usually shorter.

Fully smutted head and healthy head.  Smutted heads remain obvious up to harvest.
Photo: Evans
Picture description
Fully smutted head and healthy head. Smutted heads remain obvious up to harvest.
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Management strategy
Covered smut mainly contaminates the healthy grain during harvest and storage and loose smut is transferred to healthy grains during the growing season. For control - use seed fungicide treatment, clean seed and resistant varieties for both loose and covered smuts.

A more complete description of smut.

Loose Smut
Ustilago avenae

What to look for?
Loose smut is very similar to covered smut except that the spores are mainly dispersed to healthy grains (heads) during the growing season. By harvest, the infected heads have generally released all of their spores. Covered smut spores remain more or less intact in the diseased heads of grain until harvest. Although not usually a significant problem, oat fields with up to 70% infection have been observed with either loose or covered smut diseases in the Edmonton area.

Loose smut spores are easily dispersed during the growing season leaving bare heads.
Photo: Nielsen
Picture description
Loose smut spores are easily dispersed during the growing season leaving bare heads.
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Management strategy
Clean seed, seed treatment and resistant varieties give good control.

A more complete description of smut.

Crown Rust
Puccinia coronata f.sp. avenae

What to look for?
Crown rust is a problem where buckthorn (Rhamnus) the alternate host of this fungus occurs in eastern Canada and the eastern prairies--Manitoba and Saskatchewan. This rust can attack oats, wild oats, barley and wild grasses. Buckthorn as yet does not exist in Alberta. This alternate host was introduced from Europe into Canada and the United States as an ornamental of parks and as a hedging plant. It now grows in ravines and fields. Many races and biotypes of this fungus occur in nature.

Bright yellow rust pustules appear over whole oat plant.
Photo: Chong
Picture description
Bright yellow rust pustules appear over whole oat plant.
The alternate host stage of this fungus on buckthorn fruit.
Photo: Harder
Picture description
The alternate host stage of this fungus on buckthorn fruit.
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Management strategy
Don't bring buckthorn into Alberta!

A more complete description of crown rust.

Ergot
Claviceps purpurea

What to look for?
Ergot will show up occasionally on oat plants. The disease shows up in areas of high copper deficiency and occasionally during seasons of prolonged drought. Both of these conditions may interfere with or result in failure of pollen viability at heading causing florets to open and allowing ergot infection. Wheat, barley and oats are all self-pollenated crops with internal pollenation of flowers taking place prior to anthesis. Frost, extreme drought and severe copper deficiency can kill pollen grains. Unfertilized oat, wheat or barley flowers will then open to "look for" outside sources of pollen for the unfertilized female stigmas.

Black hard ergot on oat.
Photo: Clarke
Picture description
Black hard ergot on oat.

Management strategy
Apply copper fertilizer to the soil or to the foliage at late tillering.

A more complete description of ergot in oats.

Stem Rust
Puccinia graminis f.sp. avenae

What to look for?
Stem rust on oats, and even wild oats, is every bit as destructive on this crop as its counterpart is on wheat. The disease in the form of many races occurs annually in eastern Canada and the eastern prairie provinces.

The alternate host for this disease is common barberry which occurs in areas east of Saskatchewan and in British Columbia. While the barberry is useful for sexual reproduction and genetic change, most of the infection each year comes primarily from the U.S. Only very occasionally do we see either the stem rust of wheat or stem rust of oats in Alberta and usually only late in the season on late planted crops. As a consequence of Alberta's western "isolation" we are able to grow crown rust and stem rust susceptible oat cultivars.

Heavily rusted oat stems and leaves (brown rust urediospore stage).
Photo: Harder
Picture description
Heavily rusted oat stems and leaves (brown rust urediospore stage).
Aeciospores on the underside of a barberry leaf.
Photo: Harder
Picture description
Aeciospores on the underside of a barberry leaf.
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Management strategy
None needed in Alberta.

A more complete description of stem rust.

Common Root Rot
Cochliobolus sativus. Fusarium spp.

What to look for?
Common root rot can occur on oats but just like the take-all disease, it is of unusual occurrence on this crop in Alberta.

Oat plant with common root rot.
Photo: Duczek
Picture description
Oat plant with common root rot.
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Management strategy
None recommended.

A more complete description of common root rot.

Halo Blight
Pseudomonas syringae pv. coronafaciens or P. syringae pv. striafaciens

What to look for?
Halo blight and stripe blight occur in Alberta during warm, wet weather. Infected leaves on seedlings or older plants turn brown and die. Dry weather stops the disease.

Severely blighted leaves.
Photo: Duczek
Picture description
Severely blighted leaves.
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Management strategy
Crop rotation helps avoid build-up of this disease.

A more complete description of halo blight in oats.

Leaf Blotch
Pyrenophora avenae

What to look for?
Small red spots may appear on seedling leaves. Often the source is infected seed. Oat after oat crop can lead to a build-up of this disease which can cause blotches on the upper leaves and heads.

Small red spots on leaves.
Photo: Harder
Picture description
Small red spots on leaves.
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Management strategy
Seed treatment fungicides and crop rotation will control this disease.

Septoria Leaf Blotch
Septoria avenae f.sp. avenae (Phaeosphaeria avenaria or Stagonospora avenae)

What to look for?
Shows up when oats are grown after oats in wet and humid growing seasons. Yield loss can occur under continuous cropping.

Purple brown spots of the Septoria fungus.
Photo: Harder
Picture description
Purple brown spots of the Septoria fungus.
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Management strategy
Follow a crop rotation since the fungus survives on crop residue.

A more complete description of septoria leaf blotch in oats.

Oat Blue Dwarf
Oat Blue Dwarf Virus

What to look for?
Rare on the prairies but it can occur. This virus is transmitted by the six-spotted leafhopper. When the disease does occur it will often be in circular patches in the oat crop and infected oat crops will be severely stunted. This virus also can infect barley and flax.

Stunted distorted oat plant.
Photo: Harder
Picture description
Stunted distorted oat plant.
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Management strategy
None at present

A more complete description of blue dwarf in oats.

Brome Mosaic
Brome Mosaic Virus and Oat Necrotic Mottle Virus

What to look for?
Can be occasionally found in oat crops. Usually only one or more plants show mosaic or mottle symptoms.

Distinct mosaic pattern of the virus.
Photo: Haber
Picture description
Distinct mosaic pattern of the virus.
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Management strategy
Not really a crop loss problem.

Take-all
Gaeumannomyces graminis

Rare in oats but there are oat specific strains. Oats produce an antifungal compound avenacin which prevents take-all infection. Manganese availability or deficiency is also related to the extent of this disease syndrome.

A more complete description of take-all.

Fusarium Head Blight
(Fusarium sp. asp. F. graminearum)

What to look for?
Head infection levels can be comparable to that of wheat and barley but the loose panciles of the oat head. Keep infected florets away from healthy florets i.e. the disease does not move from floret to floret as will wheat, barley, rye and triticale.

Management strategy
See Fusarium of Barley and Wheat (Agdex 110/632-1).

A more complete description of fusarium head blight.

Alberta Fusarium graminearum Management Plan

Fusarium FAQ


Non-Infectious

Blast
Physiological

What to look for?
Blast may result from fungal or viral disease infection but usually from very hot dry growing conditions. The top oldest florets on the head may be okay but the younger lower florets may be white and sterile.

Blasted white lower florets.
Photo: Harder
Picture description
Blasted white lower florets.
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Management strategy
Oats prefer cooler moister areas of Alberta with pH levels below pH 7 preferrably around 6 to 6.5.

Gray Speck
Manganese Deficiency

What to look for?
Very common on oats growing on soils with pH levels greater than 6.5. Above 7.5, oat crops do very badly primarily due to manganese deficiency which can also occur in barley crops. Foliar applications of manganese gives good yield responses with both barley and oats.

Gray speck or yellow stippled lesions typical of manganese deficiency.
Photo: Martens-Harder
Picture description
Gray speck or yellow stippled lesions typical of manganese deficiency.

Management strategy
Avoid growing oats on soils with a pH greater than 7 or those that are naturally low in manganese.

Leaf Spot
Physiological

What to look for?
A spotting that may be caused by a deficiency of chloride. On soils with pH levels below pH5 oats just like wheat and barley suffer from aluminum toxicity. Symptoms may be highly variable. Yields losses may be very high in these acidic soils.

Chlorotic flecking possible due to chloride deficiency.
Photo: Harder
Picture description
Chlorotic flecking possible due to chloride deficiency.
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Management strategy
Add chloride in the form of potassium chloride at 10 or more pounds per acre and if the soil pH is at or below 5 then soil liming (or woodash) must be considered.

P Deficiency

What to look for?
Common on gray wooded soils low in available phosphate and deficiencies are very obvious in cold dry springs, resulting in some yield losses.

Severe phosphate deficiency.
Photo: Evans
Picture description
Severe phosphate deficiency.

Management strategy
Ensure adequate soil phosphate levels are present.

Other Diseases of Oats

Seedling Blight
Can be associated with soil-borne fungi but more commonly due to residual soil herbicides.

Aster Yellows
Not found in nature.

Oat Cyst Nematode
Very destructive on oats and wild oats but found only in Ontario, Canada and Oregon, U.S.A.

Photographs and information assembled and prepared for ARD by Dr. Ieaun R. Evans Agri-Trend Agrology Ltd.
 
 
 
 
This document is maintained by Shelley Barkley.
This information published to the web on December 2, 2003.
Last Reviewed/Revised on March 17, 2008.