Controlling Barley Diseases in Direct Seeding Systems

 
 
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 Barley diseases | Influence of tillage systems on barley disease | Direct seeding tips for disease control | More information

Disease control in barley requires proper management and sound agronomic practices no matter which tillage system is used. Weather conditions and crop rotations are usually much more influential than the tillage system in determining disease intensity in barley.

Barley Diseases

Yield- and quality-influencing infectious diseases of barley on the prairies can be divided into the categories shown in the table below.

Disease Source
Disease
Control
Seed-borne*true loose smutsystemic seed-treatment fungicides
false loose smutseed-treatment fungicides, resistant varieties
covered smutseed-treatment fungicides, resistant varieties
fungal leaf stripeseed-treatment fungicides, resistant varieties
Residue-bornenet blotchfoliar fungicides, crop rotation, resistant varieties
scaldfoliar fungicides, resistant varieties, crop rotation
speckled leaf blotch (septoria)resistant varieties, crop rotation
powdery mildewfoliar fungicides, crop rotation
ergotincrease soil copper availability, tillage
fusarium damaged kernels**seed treatment fungicides, crop rotation (avoid planting barley after cereal and corn crops)
halo spotcrop rotation
sharp eyespotcrop rotation
Soil-bornecommon root rot (seedling blight)seed-treatment fungicides, crop rotation, resistant varieties, balanced fertility
spot blotch***(smudge, black point)crop rotation, resistant varieties
take-allcrop rotation (avoid planting barley after take-all infested wheats)
Off-siterustsresistant varieties, foliar fungicides; stem and leaf rusts of barley are not normally problems in Alberta
viruses (spread by aphids, leaf hoppers, pollen and soil-borne fungi)no control available for many viral diseases, such as barley yellow dwarf; for seed-borne barley stripe mosaic virus, use pedigreed (certified) seed, which is normally free of this disease; flame chlorosis is present only in Manitoba and the United States.
*
Recommended seed treatment fungicides do not harm emergence or establishment of hulless or hulled barley cultivars.
**
Matting barley has zero tolerance for fusarium damaged kernels, and anything approaching 1% infection off fusarium damaged kernels makes any barley unsuitable for hogs and other monogastric.
***
The same fungus that causes common root rot.

Sporadic or poorly understood diseases of barley include: aster yellows, bacterial blight, blue dwarf virus, browning root rot, cephalosporium stripe and grey speck (manganese deficiency). Gray speck is a common problem on dryland barley in southern Alberta, particularly in dry summers.)

Important non-infectious diseases of barley are as follows:

  • frost banding when temperatures drop below -3°C overnight, and heat banding from hot or very bright sunlight
  • prolonged waterlogging
  • herbicide injury
  • nutrient deficiencies
Herbicide injury may resemble infectious diseases, predispose the crop to lodging (similar to sharp eyespot) or result in poor crop vigour and yield. Herbicide injury can result from herbicides applied to the crop or from herbicide residues. Severe crop injury from herbicides can result from an interaction of several factors including drought, cold temperatures, high crop residue levels, livestock manure applications, soil-borne herbicide residues and soil copper deficiency.

Copper deficiency in barley can induce many symptoms that resemble other problems, such as lodging, delayed maturity and significantly reduced yields and quality. See Copper Deficiency: Diagnosis and Correction (Agdex 532-3), Micronutrient Requirements of Crops in Alberta (Agdex 531-1) and Minerals for Plants, Animals and Man (Agdex 531-3) for more information.

Influence of Tillage Systems on Barley Disease

Seed-borne and off-site disease sources
Tillage systems have no known effect on the incidence or degree of seed-borne diseases, rusts and viral infections. All barley seed should be treated with fungicide to avoid introducing destructive seed-borne diseases or control their build-up.

Residue-borne diseases
Several major factors contribute to the increased extent and occurrence of residue-borne diseases on barley:
  • occurrence of wet or humid weather
  • presence of overwintering disease organisms
  • lack of crop rotation
  • copper deficiency causing delayed maturity
Direct seeding and other reduced tillage systems can be a secondary influence because the crop residue cover may allow a more rapid build-up of diseases such as net blotch, scald, speckled leaf blotch (septoria) and sharp eyespot under weather conditions favourable for disease build-up.

No matter what tillage system is used, a three- to four-year crop rotation provides good control of residue-borne diseases because the disease organisms in the residues usually break down before barley is grown again. Under wet or humid weather conditions, timely foliar fungicide applications may make the difference between feed and malting quality grain. In addition to improved quality, yield response following fungicide application can range from 5 to 30 per cent or more in high-input crops.

Tillage or burial of ergot bodies prevents them from germinating. However, the main factor contributing to the occurrence of ergots in wheat, barley and oats is soil copper deficiency (see Copper Deficiencies in Cereal Crops, Agdex FS532-2). Recent research also shows that low boron levels may increase ergot build-up in Quebec and Western Europe. Ergots usually originate from infected wild grasses in the field headlands. Wind and insects spread the ergot spores from germinated ergots in the headlands to nearby crops.

Diseases such as powdery mildew and halo spot are minor problems in the prairies at present. Only time will tell if direct seeding affects the occurrence or level of these diseases.

Soil-borne diseases
Agriculture and Agri-Food Canada research at Saskatoon has shown that common root rot decreases under reduced tillage. Common root rot is the only consistently destructive soil-borne disease of barley on the Canadian prairies. In Alberta, it is estimated to cause average annual yield losses of about 10 per cent. Losses in an individual field can be much higher.

Research by Agriculture and Agri-Food Canada at Lethbridge has found that common root rot of wheat is not highly infectious to barley and common root rot of barley is not highly infectious to wheat.

Common root rot has several phases including seedling blight, root rot and foliar spot blotch. Spot blotch (also called smudge) occurs when the root rot fungus attacks the leaves, stems and heads of barley. The incidence of spot blotch will likely increase if there is a heavy crop residue cover, especially if barley follows barley.

Spot blotch is destructive in eastern Canada, particularly in lodged crops. In recent years, it has been a concern in Manitoba and eastern Saskatchewan. Spot blotch can be as destructive as any foliar disease with the added disadvantage of being one of the causes of black point and the consequent downgrading of barley quality.

Agriculture and Agri-Food Canada research in Saskatchewan has shown that take-all levels decrease under reduced tillage, while research in the United States Pacific Northwest has found increased take-all levels. While highly destructive on wheat, take-all is not often as destructive on barley. However, it is not recommended to plant barley after wheat that was heavily infested with take-all.

Direct Seeding Tips for Disease Control

Crop rotation
Crop rotation plays a major role in effective disease control in barley, whether direct seeding or conventional tillage is used. Growing barley in a three- to four-year rotation will eliminate or effectively control most soil-borne and residue-borne diseases, including major diseases such as scald, net blotch and root rot.

Producers continuously growing barley or using short rotations will need to pay special attention to soil fertility, resistant barley varieties and fungicidal disease control. Growing barley continuously generally results in significantly reduced yields and lower quality grain, especially in the wetter, higher yielding areas of Alberta. Since many root, foliar and head diseases are involved, yield losses in the order of 20 to 30 per cent are not uncommon.

Crop residue effects
  • The crop residue cover on direct seeded fields conserves soil moisture and traps snow. Thus, seeding depths can be shallower in direct seeded fields. Shallow seeding may result in earlier emergence, leaving more energy for healthier seedlings better able to withstand disease.
  • Direct seeding avoids the marked temporary nitrogen deficiency in conventional tillage fields caused by incorporating large amounts of straw into the soil immediately before seeding. Thus, direct seeding can give barley seedlings a better start for a healthier stand.
  • A crop residue cover may result in cooler spring soil temperatures. Thus, in cool, wet springs, direct seeding may result in a greater delay in crop emergence (see Soil Temperature and Direct Seeding, Agdex 590-2).
More Information

For more information on barley diseases, please refer to the following publications:
Another useful reference is a symposium paper by K.L. Bailey and L.J. Duczek entitled "Managing Cereal Diseases under Reduced Tillage" (Canadian Journal of Plant Pathology, 1996, volume 18, pages 159-167).

Prepared by:
Dr. I. Evans

Source: Agdex 519-13. Revised July 1999.
 
 
 
 
For more information about the content of this document, contact Duke.
This information published to the web on July 1, 1999.