Bacterial blight is a disease of

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

caused by the bacterial pathogen ''Xanthomonas campestris'' pv. ''translucens'' (syn. '' X. translucens''). It has been known as a disease since the late 19th century. It has a worldwide distribution.

Symptoms

The disease is characterized by small, pale green spots or streaks which soon appear water-soaked. The

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by injury or diseases. The term ''Lesion'' is derived from the Latin meaning "injury". Lesions may occur in both plants and animals. Types There is no de ...

s expand and then appear as dry dead spots. The lesions elongate into linear streaks which may eventually extend the full length of the

leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...

. Lesions rarely occur on the leaf sheath or culm. In severe infections, a milky gray exudate may be squeezed from the cut end of leaf exhibiting symptoms. Brown spots on the margin of the cotyledon characterized plants

Disease cycle

This disease is caused by a common

bacterium Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the ...

that persists in soil and water and is spread by wind-driven rains. The bacteria overwinters on crop residue, seed, fall-sown cereals, and

perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...

grasses. Spring infection may result from any of these sources. Subsequent infections are spread by splashing of bacterial ooze by rain drops, plant to plant contact and insects. Bacterial blight develops on the upper leaves of during periods of cool, wet weather, after the plants have reached the boot stage. Leaf

blight Blight is a specific symptom affecting plants in response to infection by a pathogenic organism. Description Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. A ...

is associated with high

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...

, wet weather, and cool spring temperatures (15–25 degrees C or 60–75 degrees F). Warm, dry weather stops the disease and new emerging leaves may be relatively free of bacterial infection.

Crop loss

Although detailed studies have not been conducted, damage to the

flag A flag is a piece of textile, fabric (most often rectangular) with distinctive colours and design. It is used as a symbol, a signalling device, or for decoration. The term ''flag'' is also used to refer to the graphic design employed, and fla ...

often occurs suggesting that yield losses may reach 10–15%.

Management

Disease incidence and severity is reducing by rotating to non-grain

crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. In other words, a crop is a plant or plant product that is grown for a specific purpose such as food, fibre, or fuel. When plants of the same species a ...

, burying crop residue and using disease free seed. No resistant cultivars are known, some are more susceptible than others.

References

External links

Bacterial blight (Canada: Manitoba)

{{DEFAULTSORT:Bacterial Blight (Barley) Bacterial plant pathogens and diseases Barley diseases