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Week 5 (unit 9)

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Barley, Rye and Oats

Origin, taxonomy, and genetic systems
Growth requirements, physiological and adaptive traits
Production statistics, economics and marketing
Quality factors for malting, brewing, and other end-uses
Major diseases and insect pests
Genetic resources and breeding

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Barley (Hordeum vulgare L.) ranks fourth among the cereals in worldwide production. It is an important crop for direct human consumption and for animal feed. It is unique as a source of malt for beer and other products.



Photo courtesy Patrick Hayes, OSU

Origin, Taxonomy, and Genetic Systems of Barley

Barley was one of the first domesticated cereals, most likely originating in the Fertile Crescent area of the Near East. Many references to barley and beer are found in early Egyptian and Sumerian writings that are more than 5000 years old. Archaeological evidence of barley cultivation has been found dating back to 8000 BC in Iran. There is now considerable evidence that the initial cultivation of barley in China and India occurred at a later date.

Cultivated barley is one of 31 Hordeum species, belonging to the tribe Triticeae, family Poaceae. It is an annual diploid species with 2n=14 chromosomes. The genetic system is relatively simple, while the species is genetically diverse, making it an ideal study organism. Molecular evidence has revealed considerable homology between barley, wheat, and rye. Among the wild Hordeum, there are diploid, tetraploid, and hexaploid species. Many are perennial. The species are native in various parts of the world.

Barley has a single floret in each spikelet. There are three spikelets at each node, alternating on opposite sides of the barley head or spike. In two-rowed barley, the central floret is fertile and the two lateral florets are sterile, resulting in a single seed at each node, giving the head a flat appearance (see the picture on the far right). In six-rowed barley, all of the florets are fertile (see the head on the left side of the picture). The central seeds are round and fat, but the laterals tend to be slightly asymmetric. A single head of barley can produce up to 80 seeds. 6 row and 2 row Barley. Photo: U. Minnesota Extension Service
Photo Courtesy of the University of Minnesota Extension Service

Currently the wild ancestor of barley (H. vulgare subsp. spontaneum) is thought to be a subspecies of cultivated barley, and cultivated barley is classified in the subspecies vulgare. Wild barley has a brittle rachis and occurs only in the two-row form. Cultivated barley has a nonbrittle rachis and may be two-rowed or six-rowed. H. vulgare subsp. spontaneum may be a transitional form between the true progenitor of barley and the cultivated species.

Barley generally has several stems or tillers. The tillers are round and erect, with conspicuous nodes and internodes. Like many grasses, the stem is hollow. The ability of the barley plant to send up new tillers in response to favorable environmental conditions is a useful mechanism for adapting to changes during the growing season.

Two-rowed varieties usually have a higher number of tillers per plant and larger, heavier seed than six-rowed varieties. Six-rowed varieties on the other hand, usually have more seeds per inflorescence. Thus the compensatory effects of yield components lead to similar levels of yield potential.

The straw of barley is generally weaker than wheat.


Growth Requirements, Adaptive Traits, Management Practices

While claims are often made about the wide adaptability of various cereal crops, barley may well be the champion. It is grown in a range of extreme environments that vary from northern Scandinavia to the Himalayan mountains to monsoon paddies. It is particularly noted for its tolerance to cold, drought, alkali, and salinity. Its rapid growth enables it to compete well with weeds and other grasses. It is earlier in maturity than wheat and other cereal crops. It is not well adapted to acid soils and wet conditions.


Photo courtesy Patrick Hayes, OSU

Requirements for inputs, particularly nitrogen, are relatively low. Barley should be grown under moderate nitrogen fertility conditions because high fertility will reduce kernel plumpness and increase lodging. The grain protein target for malting barley is 11.5% to 13%, which must also be considered in determining appropriate nitrogen fertilizer levels.

As a C3 plant, barley favors cool production conditions (15-30 °C) and moderate precipitation (500 - 1000 mm annually). Cultivars that are photoperiod sensitive require long days to flower. Both winter and spring habit types exist. For winter barley, a vernalization period of two to ten weeks below 50 °F is necessary. In general, winter barley genotypes are not as cold hardy as winter wheat. Highest commercial yields tend to come from central and northern Europe, where yields of 10 t/ha can be obtained under intensive management.

No barley variety is adapted to all environments and, in fact, very different gene pools have evolved in the major barley production areas of the world. The gene pools may be defined by essential physiological parameters that determine adaptation to a production environment - such as vernalization and/or photoperiod response - or they may be defined by evolutionary bottlenecks and the accidents of history, such as regional preferences for two-rowed or six-rowed varieties.

Types of barley

  • Feed and malt types
  • Hulled and hulless varieties
    • hulled types - the lemma and palea remain attached to the seed at maturity
      Hulled barley is the predominant type in the US and many other parts of the world.
    • hulless types - the seed threshes free of the lemma and palea (hull)
      Hulless barley is produced for various food and beverage uses in East Asia (primarily, China, Japan, and Korea). Hulless barley is an important subsistence crop in the Andes and Himalayan regions and in Ethiopia. In Canada, hulless varieties are commonly grown as feed for swine.
  • Awned types predominate
    • Rough and smooth awn types
    • Hooded (modified awns) are used for silage and green chop
    • Awnless types exist

    Awned barley
    (Courtesy Patrick Hayes, OSU)

    'Sara' hooded barley
    (Courtesy Patrick Hayes, OSU)

  • Aluerone color variations
    • colorless
    • white
    • yellow
    • blue
  • Waxy starch type (100% amylopectin) - used for specialty food and feed
  • Dwarf types are common; Taller types are used in rain-fed production regions

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Production Statistics, Economics and Markets

Barley ranks fourth among the cereals in terms of total world production. The average production from 2000-2002 was 136,270,100 metric tonnes. The map below shows the distribution of production by country over the same time period.


Barley Prodcution around the world. Three Year average. Data source: FAOSTAT.

Countries that Produced the Most Barley (3-year averages, 2000-2002)
(ha x 1,000)
(Mt x 1,000)
Russian Federation
United Kingdom
United States

Leading Barley Import and Export Countries (Averages for 1998-2000)
(Mt x 1,000)
(Mt x 1,000)
Saudi Arabia
Russian Federation
  United Kingdom
  United States
United States


Barley Production in the United States

  • US production averages 400 million bushels per year with an annual value of $923 million as a raw commodity (1988 - 1997).
  • Of the barley consumed domestically, approximately
    • 55% of the barley crop is used for animal feed
    • 39% for malt production
    • 3.5% as seed
    • 1.7% in food products
  • Total value of the annual barley crop is
    • $184 million for barley and milled products
    • $48 million for malt and malt extracts
    • $332 million for beer.
  • US production represents 5-10% of the world production.
  • Largest importers of US barley are Japan and Mexico.

Major barley production areas in the USA by county

Historically, the production of malt has continued to shift to the west over time. This trend was
accelerated by the epidemic of Fusarium head blight (Fusarium graminearum) in the upper Midwest. Idaho and the Pacific Northwest are increasingly important areas for malt barley production.

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Quality Factors for Malting, Brewing and other End-uses

Barley is primarily used for animal feed. It is fed to beef cattle, dairy cattle, swine and poultry. In most cases, the whole barley kernel is rolled, ground, or flaked, prior to being fed. Feed efficiency improves with removal of hulls, grinding, or breaking of the bran layer (efficiency = weight gain / weight fed).

  • Dry rolling: cheap, but dusty
  • Steam rolling: same efficiency, but better palatability
  • Fine grinding: hammer mill for impact grinding
  • Pelleting: force material through die

The second most important use of barley is for malt. Malt is used in beer, liquor, malted milk and flavorings in a variety of foods.

Barley is also used for food. Pearling barley involves removal of the hull by using abrasive rollers with paddles moving through a perforated steel cylinder.

There is increasing interest in barley for food uses, because barley fiber has been shown to reduce cholesterol and the associated risk of cardiovascular disease. Beta-glucan (soluble fiber) is found throughout the barley kernel, not just in the bran, so the health benefits of barley in the diet are retained even when the bran is removed. The US Food and Drug Administration (FDA) authorized use of a health claim for barley in reducing the risk of coronary heart disease in 2005. The claim is based on consumption of three grams of beta-glucan daily.

U.S. Barley Grades are based on:

  • Row number (2-row vs 6-row)
  • Malt vs feed use
  • Test weight (minimum of 50 lbs/bu for US No. 1 two-rowed malting barley, 47 lbs/bu for US No. 1 six-rowed malting barley and feed barleys; a bushel of barley = 48 lbs)
  • Discount schedule
  • Plumps: percent (by weight) of grain retained on 6/64” x 3/4" slotted screen
  • Thins:
    • percent passing through 5/64” screen for 6-row
    • percent passing through 5.5/64" screen for 2-row

Generally higher test weight and greater percent plumps indicate better feed value and better malt quality.

Barley for malting

Two-rowed barleys are favored for malting throughout most of the world, but in the USA and Mexico, six-rowed barleys are used extensively for this purpose. Thus, there are no absolute definitions of malting and brewing quality, due to differences in malting and brewing practices and consumer preferences.

The American Malting Barley Association (AMBA) provides specific quality guidelines for breeders in the US market: http://www.ambainc.org/ni/index.htm

Contract production for malting: specifications are given to growers for grain quality, plump kernels, and protein content.

The malting process

Source: http://www.howtobrew.com/section2/chapter12.html

The starch, protein and nucleic acid molecules that are stored in barley grains are not good nutrients for brewing yeast nor do they support the fermentation reactions performed by brewing yeasts. These large and structurally complex compounds must be partially or, in some instances, fully degraded into their component sugars, amino acids, and nucleotides before the yeast can use them. When barley seeds germinate, hydrolytic enzymes are synthesized or converted to active forms that can readily degrade these large compounds.

Malting is controlled sprouting - A complex interaction of genes involved in germination, growth and development.

Steps in malting:

  1. Steep: raise moisture to 42-44% uniformly through kernel
    • If too short – poor malt
    • If too long – mold and bacteria grow
  2. Germination : on beds with forced air and 100% RH at a temperature of 15 °C.
    Releases alpha-amylase, beta-amylase, glucosidase, and dextrinase.
    These enzymes are temperature stable during drying (kilning).
  3. Kilning : reduces moisture and dries malt
  4. Browning : adds flavor and color
  5. Optional bleaching : reduces color

Changes in kernel composition and enzymes during malting

grain changes during malting

During malting, the acrospire (the plant shoot) grows along one side of the kernel. As it grows, pre-existing enzymes are released and new enzymes are created in the aleurone layer which "modify" the endosperm (the protein/carbohydrate matrix starch reserve) for the acrospire's use.

Malted barley is the source of the sugars (principally maltose) which are fermented into beer. The grain partially germinates, releasing enzymes in the aleurone layer (outermost layer of the endosperm). New enzymes are created that break down the endosperm's protein/carbohydrate matrix into smaller carbohydrates, amino acids and lipids, and open up the seed's starch reserves. The endosperm is composed of large and small starch granules that are packed in a protein matrix. The cell walls within the matrix holding the starch granules are primarily composed of beta-glucans (a type of cellulose), some pentosans (gummy polysaccharide) and some protein. The degree to which the enzymes unpack the starch granules (i.e. breakdown the endosperm) for use by the growing plant (or brewers) is referred to as the "modification." It refers to all of the polymer-degrading processes that occur during malting.

One visual indicator that a maltster uses to judge the degree of modification is the length of the acrospire which grows underneath the husk. The length of the acrospire in a fully modified malt will typically be 75-100% of the seed length. Drying is used to stop the malting process when the proper balance between resources converted by the acrospire and resources consumed by the acrospire has been achieved.

The purpose of malting is to create these enzymes, break down the matrix surrounding the starch granules, prepare the starches for conversion, and then stop this action until the brewer is ready to utilize the grain. After modification, the green malt is gently dried with heat (kilning) and the acrospire and rootlets are knocked off by tumbling. The kiln drying of the new malt denatures many of the enzymes, but several types remain, including the ones necessary for starch conversion. The amount of enzymatic starch conversion potential that a malt has is referred to as its "diastatic power".

Beta glucans are the soluble dietary fiber component of barley and oat bran. Beta-glucan is thought to have serum cholesterol reducing properties and occurs in highest amounts in the endosperm of barley and oats. Beta-glucan also is important for the malting industry and indicates how well the endosperm is modified. High levels of beta-glucan cause a viscous wort that may cause problems with filtration or hazy beer. Thus, lower levels of beta-glucan are preferred for brewing.


Steps in Brewing

1. Malted barley is soaked in hot water to release the malt sugars.
2. The malt sugar solution is boiled with hops for seasoning.
3. The solution is cooled and yeast is added to begin fermentation.
4. The yeast ferments the sugars, releasing CO2 and ethyl alcohol.
5. When the main fermentation is complete, the beer is bottled with a little bit of added sugar to
provide the carbonation.

Mashing - the hot water soaking process that provides the right conditions for the enzymes to convert the grain starches into fermentable sugars. The basic light colored malts such as pale ale malt and pilsener malt need to be mashed to convert the starches into fermentable sugars.

Adjuncts - fermentables not derived from malted barley.

Extract efficiency - typical amount of fermentable and non-fermentable sugars obtained from the grain.

German or US specialty beers use straight barley malt. Most brewers use adjuncts of rice, corn, wheat, or other grits to provide an additional carbohydrate source. Hops are added for ‘bitters’. Yeast is Saccharamyces carlsbergensis, occasionally S. cerevisiae.

The malt is treated with water under appropriate conditions (“mashing”) to obtain an extract (wort) that must perform several critical functions.

  1. The extract must provide adequate nourishment to the yeast so that fermentation can occur.
  2. The extract must provide sufficient fermentable sugars to enable the yeast to produce the desired levels of alcohol.

A high quality malt will contain the right amount of hydrolytic enzymes and metabolites to fulfill these requirements and will have the right degree of friability to allow many of its components to be readily solubilized during mashing. During malting and mashing, the barley starch should be almost completely degraded into sugars that can be utilized by the brewing yeasts, whereas only about 45% of the barley protein should be solubilized. Too much protein solubilization is thought to result in beers with poor foaming characteristics. When insufficient protein hydrolysis occurs, the remaining proteins may interact with polyphenols to form beer haze precipitates.

Four amylolytic enzymes are generally thought to participate in converting the starch in malted barley into fermentable sugars: these are alpha-amylase, beta-amylase, alpha-glucosidase and limit dextrinase. During brewing, amylase enzymes digest amylose (linear starch) and amylopectin (branched starches) into hexose sugars. The sugars are a nutrient source for the yeast to facilitate fermentation. Sufficient sugars are needed to obtain the desired alcohol level.


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Barley Diseases and Pests

Barley is affected by many diseases, most of which are typical of small grain cereals, e.g., rusts (Puccinia spp), smuts (Ustilago spp), root rots (Rhizoctonia, Pythium, Fusarium), bacterial blights and viruses.

In the US, there are fewer problems with disease and insect pests in the western states, where production conditions are drier with low relative humidity.

Major diseases

Source: http://plant-disease.ippc.orst.edu/plant_index.cfm

Barley yellow dwarf virus (BYDV)

BYDV is spread by several species of aphid. Symptoms can be variable and may be confused with nutrient deficiencies or stress. The severity of the damage will also be variable, depending on the susceptibility of the variety, virulence of the strain, the time of infection, and environmental conditions. The disease is most severe when the weather is cool and moist. The virus can be avoided to some extent by planting very early in the spring or late in the fall. Use of resistant varieties or systemic insecticides also provide control.

Fusarium head blight or scab (FHB)


FHB is a fungus that attacks both wheat and barley. Within the last dozen years there have been outbreaks of FHB in the Midwestern and Eastern states of the USA, as well as in Central and Eastern Canada. FHB is increasingly threatening wheat and barley food supplies worldwide.

There are several Fusarium species that can cause FHB, but the one that has been problematic in the Midwest in recent years is F. graminearum. Spread of the disease is favored by extended wet periods.

The damage due to the pathogen is two-fold. Infested cereals show significant reduction in seed quality and yield due to discolored, shriveled "tombstone" kernels, and secondly, scabby grain is often contaminated with mycotoxins making it unsuitable for food, beer production, or feed.
The U.S. Wheat and Barley Scab Initiative (USWBSI) is a major initiative that aims to develop effective control measures as quickly as possible.

Barley stripe rust (BSR)

Source: http://www.ars.usda.gov/is/AR/archive/aug99/barley0899.htm

Barley stripe rust is caused by a fungus Puccinia striiformis f. sp. hordei that was accidently introduced from Europe into South America in 1975. It first appeared in the US in 1991. It is particularly devastating in the cool, moist environments in the Pacific Northwest.

BSR spreads by powdery, yellow spores. The spores are produced in large, yellow stripes between leaf veins, giving the leaves a striped, rusty appearance. When infection is severe, losses of 50% are common. Resistant cultivars are available, and efforts are underway to develop adapted, malting varieties with resistance for the PNW.

Photo courtesy Patrick Hayes, OSU


Important insect pests of barley include:

  • Green bug (Toxoptera graminum)
  • Russian wheat aphid (Diuraphis noxia)
  • jointworm (Tetramesa hordei)
  • cereal leaf beetle (Oulema melanopus)
  • Barley thrips (Limothrips denticornis)
  • aphids

Most of these pests also attack wheat and other cereal crops.

The University of Idaho has developed an on-line key for identification of important insect pests in field crops in the Pacific Northwest (http://info.ag.uidaho.edu/keys/plates/plates_contents.htm).

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Genetic Resources and Breeding

There is extensive natural variation in barley, which makes it quite responsive to artificial selection.

Major germplasm collections

  • USDA National Small Grains Collection
  • Canada's Plant Gene Resources
  • Nordic Barley Gene Bank (Sweden)
  • ICARDA (Syria)
  • Major collections in Germany, Japan, and the former Soviet Union

In the USA - Feed barley development resides largely in the public sector, whereas development of malt types occurs primarily in the private sector.

Hulless (naked) barley - controlled by a single recessive gene that can be easily incorporated into adapted germplasm. Hulless types are not suitable for malting.

Waxy types - controlled by a single gene that imparts 100% amylopectin starch.

Breeding and selection for malt quality

  • Evaluations are expensive, limiting number of assays possible
  • USDA-ARS lab in Madison, WI
  • Micro-malting tests, enzyme assays
  • Pilot-plant brewing
  • Malt-house trials
  • Final: taste tests
  • Variety development: often 15 yr process
  • Final release of malting variety is highly dependent on ‘product quality’ assessments. A poor sample, poor malt, or poor taste test can kill a potential variety.

Breeding strategies

A common strategy in breeding programs is to breed for good malting quality, with the expectation that resulting varieties will also be good for feed if they do not meet the stringent requirements of the malting industry.

The most common breeding approach is to develop pureline varieties using conventional breeding techniques. At least five generations of self-pollination are required to obtain the desired level of homozygosity, beginning with the F1 cross. At OSU, doubled haploid techniques and tissue culture have been used to rapidly develop homozygous purelines (they are obtained in a single generation from the F1 cross).

Funding for barley improvement

The American Malting Barley Association (AMBA) has been highly successful in securing support through industry support and activities of a full-time director.

Examples: scab initiative, genomics funding, support for NSGC at Aberdeen, funding for ARS quality labs.

For information about barley genetic research and breeding at Oregon State University, see the BarleyWorld website.

Barley straw

There is some evidence that barley straw can be used to control algae in ponds. For information about research on this topic at OSU and for additional links and references, see the BarleyWorld website.

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Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished. http://www.hort.purdue.edu/newcrop/duke_energy/Secale_cereale.html

Wheat and Rye Leavened Bread. Source: ARS USDA Photo Gallery Rye (Secale cereale L.) is a tall annual grass probably originating from Southwestern Asia, now widely cultivated in temperate regions of the world. In general, rye varieties are tolerant to many adverse conditions. Many farmers put rye in their worst soils, since it tends to do better than other cereals under such conditions.

Rye is cultivated to produce flour and for fermentation in the production of whisky. Rye is also mixed with other grains for livestock feed. A substantial amount of the rye that is produced is used as pasture, hay, or as a cover crop rather than for grain.

Although rye does not develop true gluten, it has proteins which give it the capacity for making a nutritious leavened bread. Rye is usually mixed with 25 to 50% wheat flour for bread making.

Plant breeders have created an intergeneric hybrid between rye and wheat known as Triticale. The initial hybrid is sterile, so the chromosomes are doubled to generate a fertile polyploid that can undergo normal meiosis. The goal is to combine the grain quality, productivity, and disease resistance of wheat with the vigor and hardiness of rye.

The most serious diseas of rye is ergot (Claviceps purpurea). This disease affects other cereal crops as well, but rye is particularly susceptible. Ergot produces alkaloids that are toxic to humans and animals, resulting in a disease known as ergotism. Symptoms may vary depending on the prevalence of particular alkaloids. Ergotism is thought to be one of the causal factors of the "Holy Fire" and "St. Anothony's Fire" that were common afflictions of people during the Middle Ages. See http://www.botany.hawaii.edu/faculty/wong/BOT135/LECT12.HTM for more information about the history of ergotism.


Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished. http://www.hort.purdue.edu/newcrop/duke_energy/Avena_sativa.html


Oat (Avena sativa L.) is an annual grass species. Oat grain grows in a characteristic terminal panicle. This crop is believed to be derived from two species, wild oat (Avena fatua) and wild red oats (A. sterilis).

Oats are cultivated in temperate zones. They thrive in cool climates with long days, in areas with well drained and good (but not excessive) soil fertility. Most varieties are classified as winter or spring oats.

Oats are cultivated for grain, hay, and as a winter cover and pasture crop. Oats are used in the production of breakfast cereals, cakes, biscuits and other pastries. They are also a source of an oil. The hulls are used in the production of furfural, an important industrial chemical. Oat flour inhibits rancidity and increases the length of shelf-stability of milk, milk products, bacon, frozen fish, and vegetable oils.

Oats have long been recommended as a good source of soluble dietary fiber, which helps to lower cholesterol. Recent research indicates that oats also contain flavonoid compounds that act as antioxidants and may help to prevent heart disease and cancer.

Hot dry weather just before heading causes heads to blast and yields to decrease. To reduce problems of volunteer oats growing in the subsequent crop, oats should not be followed by another cereal crop. Rotations with non-cereal crops will also help to reduce the incidence of fungal diseases in oats.

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Group Project Assignment

Go to the Discussion Board and join a group for the Group Project is you haven't already done so.


Take the quiz on this Unit on the Blackboard.


American Malting Barley Association (AMBA). http://www.ambainc.org/

BarleyWorld. 2005. Web site of the Barley project at Oregon State University.

Center for New Crops & Plant Products, Purdue University. 2004. Avena sativa L.

Center for New Crops & Plant Products, Purdue University. 2004. Secale cereale L.

Hayes, P.M., A. Castro, L. Marquez-Cedillo, A. Corey, C. Henson, B.L. Jones, J. Kling, D. Mather, I. Matus, C. Rossi, and K. Sato. 2003. Genetic diversity for quantitatively inherited agronomic and malting quality traits. In R. von Bothmer, H. Knüpffer, T. van Hintum, and K. Sato (eds.), Diversity in Barley (Hordeum vulgare L.). Elsevier Science Publishers, Amsterdam. pdf file

National Barley Foods Council. 2005. BarleyFoods website. http://www.barleyfoods.org/

Nilan, R.A., and S.E. Ullrich. 1993. Barley: Taxonomy, origin, distribution, production, genetics, and breeding. In W. MacGregor and R.S. Bhatty (eds.) Barley chemistry and technology. American Association of Cereal Chemists, Inc., St. Paul, MN.

US Barley Genome Project. 2005.

Oelke, E.A., E.S. Oplinger, H. Bahri, B. R. Durgan, D. H. Putnam, J.D. Doll, and K.A. Kelling. 1990. Rye. Alternative Field Crops Manual. University of Wisconsin Cooperative Exension and the University of Minnesota Extension Service.

Oregon State University Extension Service. On-line guide to disease control.

Palmer, J. 1999. How to Brew. http://www.howtobrew.com/

Washington Barley Commission. 2005. http://www.washingtonbarley.org/mainset.html

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