Wheat diseases

Main article: List of wheat diseases

Additional recommended knowledge

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Weighing the right way

In Europe

Cereals are at risk from numerous diseases due to the level of intensification necessary for profitable production since the 1970s. More recently varietal diversification, good plant breeding and the availability of effective fungicides have played a prominent part in cereal disease control. Use of break crops and good rotations are also good cultural control measures. The demise of UK straw burning in the 1980s also increased the importance of good disease control.

Active control measures include use of chemical seed treatments for seed-borne diseases and chemical spray applications for leaf and ear diseases. Development of resistance by diseases to established chemicals has been a problem during the previous 30 years.

Fungicides

Some cereal fungicide groups and examples of active ingredients:

• Benzimidazoles
  • carbendazim

• Ergosterol biosynthesis inhibitors
  • prochloraz
  • flutriafol
  • tetrachonazole

• Morpholines
  • fenpropimorph

• Strobylurines
  • kresoxim-methyl

• Phthalonitriles
  • chlorothalonil

Principal diseases

• Barley yellow dwarf virus, BYDV
• Brown rust Puccinia recondita
• Bunt (see covered smut) Tilletia caries
• Ergot Claviceps purpurea
• Eyespot Pseudocercosporella herpitrichoides
• Leaf spot, glume blotch, see wheat septoria, septoria nodorum, septoria tritici
• Mildew (see cereal mildew) Erysiphe graminis
• Seedling blight Fusarium spp., Septoria nodorum
• Sharp eyespot Rhizoctonia cerealis
• Take-all Gaeumannomyces graminis
• Yellow rust Puccinia striiformis
• Tan Spot "Pyrenophora tritici-repentis"

References

Cereal Pests and Diseases (Gair, Jenkins, Lester) 1987 Farming Press ISBN 0-85236-164-5

In the USA

Wheat is subject to more diseases than other grains, and, in some seasons, especially in wet ones, heavier losses are sustained from those diseases than are in other cereal crops. Wheat may suffer from the attack of insects at the root; from blight, which primarily affects the leaf or straw, and ultimately deprives the grain of sufficient nourishment; from mildew on the ear; and from gum of different shades, which lodges on the chaff or cups in which the grain is deposited.

Examples of wheat diseases:

Bacterial diseases

• Bacterial leaf blight Pseudomonas syringae subsp. syringae
• Bacterial sheath rot Pseudomonas fuscovaginae
• Basal glume rot Pseudomonas syringae pv. atrofaciens
• Black chaff = bacterial streak Xanthomonas campestris pv. translucens
• Pink seed Erwinia rhapontici

Fungal diseases

• Alternaria leaf blight Alternaria triticina
• Anthracnose Colletotrichum graminicola
• Ascochyta leaf spot Ascochyta tritici
• Black head molds = sooty molds Alternaria spp., Cladosporium spp.
• Common bunt = stinking smut T. tritici, T. laevis
• Downy mildew = crazy top Sclerophthora macrospora
• Dwarf bunt Tilletia controversa
• Ergot Claviceps purpurea
• Foot rot = dryland foot rot Fusarium spp.
• Leaf rust = brown rust Puccinia triticina
• Leaf and glume blotch, Stagonospora nodorum or Phaeosphaeria nodorum
• Pink snow mold = Fusarium patch Microdochium nivale
• Powdery mildew = Blumeria graminis
• Scab = head blight Fusarium spp., Gibberella zeae,
• Septoria blotch Septoria tritici = Mycospharella graminicola,
• Smut = Ustilaginomycotina clade of the class Teliomycetae, subphylum Basidiomycota
• Storage moulds Aspergillus spp., Penicillium spp.
• Wheat mildew
• Wheat leaf rust
• Wheat stem rust

Nematodes, parasitic

• Grass cyst nematode Punctodera punctata
• Root gall nematode Subanguina spp.

Viral diseases and viruslike agents

• Agropyron mosaic genus Rymovirus, Agropyron mosaic virus (AgMV)
• Barley stripe mosaic genus Hordeivirus, Barley stripe mosaic virus (BSMV)
• Oat sterile dwarf genus Fijivirus, Oat sterile dwarf virus (OSDV)
• Tobacco mosaic genus Tobamovirus, Tobacco mosaic virus (TMV)
• Wheat dwarf genus Monogeminivirus, Wheat dwarf virus (WDV)
• Wheat yellow mosaic Wheat yellow mosaic bymovirus

Phytoplasmal diseases

• Aster yellows phytoplasma

Link between air pollution and septoria blotch

A team of researchers examined a library of British wheat samples dating back to 1843. For each year, they determined the levels of Phaeosphaeria nodorum and Mycospharella graminicola DNA in the samples. After accounting for influences such as growing and harvesting methods and weather conditions, they compared the DNA data with estimates of emissions of air pollutants. The effect of sulfur dioxide correlated with the abundance of the two fungi. P. nodrum grew more successful with the dawn of the Industrial Revolution. M. graminicola was more abundant before 1870 and since the 1970s. The success since the 1970s may be linked to reductions in sulfur dioxide emissions due to environmental regulations. (Bearchell, et al., 2005)

References

• Sarah J. Bearchell, Bart A. Fraaije, Michael W. Shaw and Bruce D. L. Fitt (2005). "Wheat archive links long-term fungal pathogen population dynamics to air pollution". Proceedings of the National Academy of Sciences 102 (April 12): 5438-5442 Abstract.

See also