Fire blight

Taxobox
color = lightgrey
name = "Erwinia amylovora"
regnum = Bacteria


phylum = Proteobacteria
classis = Gamma Proteobacteria
ordo = Enterobacteriales
familia = Enterobacteriaceae
genus = "Erwinia"
species = "E. amylovora"
binomial = "Erwinia amylovora"
binomial_authority = (Burrill 1882) Winslow "et al." 1920

Fireblight is a contagious disease affecting apples, pears, and some other members of the family Rosaceae. It is a serious concern to producers of apples and pears. Under ideal conditions, it can destroy an entire apple or pear orchard in a single growing season.

The causal pathogen is "Erwinia amylovora", a Gram-negative bacterium in the family Enterobacteriaceae. Pears are the most susceptible, but apples, crabapples, quinces, hawthorn, cotoneaster, pyracantha, raspberry and some other rosaceous plants are also vulnerable. The disease is believed to be indigenous to North America, from where it spread to most of the rest of the world. Fireblight is not believed to be present in Australia and Japan.

Symptoms

Fireblight is a systemic disease. The term "fireblight" describes the appearance of the disease, which can make affected areas appear blackened, shrunken and cracked, as though scorched by fire.

Primary infections are established in open blossoms and tender new shoots and leaves in the spring when blossoms are open.

Dissemination

Honeybees and other insects, birds, rain and wind can transmit the bacterium to susceptible tissue. Injured tissue is also highly susceptible to infection, including punctures and tears caused by plant-sucking or biting insects. Hailstorms can infect an entire orchard in a few minutes, and growers do not wait until symptoms appear, normally beginning control measures within a few hours.

Once deposited, the bacterium enters the plant through open stomata and causes blackened, necrotic lesions, which may also produce a viscous exudate. This bacteria-laden exudate can be distributed to other parts of the same plant or to susceptible areas of different plants by rain, birds or insects, causing secondary infections. The disease spreads most quickly during hot, wet weather and is dormant in the winter when temperatures drop. Infected plant tissue contains viable bacteria, however, and will resume production of exudate upon the return of warm weather in the following spring. This exudate is then the source for new rounds of primary infections.

The pathogen spreads through the tree from the point of infection via the plant's vascular system, eventually reaching the roots and/or graft junction of the plant. Once the plant's roots are affected, the death of the plant often results. Over pruning and over fertilization (especially with nitrogen) can lead to watersprouts and other midsummer growth that leave the tree more susceptible.

Treatment

Sprays of the antibiotics streptomycin or terramycin can prevent new infections. The use of such sprays has led to streptomycin-resistant bacteria in some areas, such as California and Washington. Certain biological controls consisting of beneficial bacteria can also prevent fireblight from infecting new trees. The only effective treatment for plants already infected is to prune off the affected branches and remove them from the area. Plants or trees should be inspected routinely for the appearance or new infections. The rest of the plant can be saved if the blighted wood is removed before the infection spreads to the roots. It is recommended to cut 30-50 cm away from the affected area as this tissue, while asymptomatic, may still contain viable bacteria. If pruning multiple plants, thoroughly disinfect cutting tools between cuts.

References

* [http://www.defra.gov.uk/planth/pestnote/fireblight.pdf "Fireblight"] by Department for Environment, Food and Rural Affairs


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Look at other dictionaries:

  • fire-blight — fireˈ blight noun A bacterial disease of fruit trees, giving a scorched appearance • • • Main Entry: ↑fire …   Useful english dictionary

  • fire blight — fire′ blight n. ppa a disease of fruit trees, esp. of pears and apples, that blackens the foliage and is caused by a bacterium Erwinia amylovora[/ex] …   From formal English to slang

  • fire blight — ☆ fire blight n. a disease of fruit trees, as the pear or apple, caused by a bacterium (Erwinia amylovora): it kills the branches and blackens the leaves …   English World dictionary

  • fire blight — noun a disease blackening the leaves of pear and apple trees • Syn: ↑pear blight • Hypernyms: ↑leaf blight • Hyponyms: ↑blight canker * * * noun 1. : a destructive highly infectious disease of …   Useful english dictionary

  • fire blight — Plant Pathol. a disease of pears, apples, quinces, etc., characterized by blossom, twig, and fruit blight and stem cankers, caused by a bacterium, Erwinia amylovora. [1740 50; from the burnt look of the foliage] * * * ▪ disease  plant disease… …   Universalium

  • fire blight — noun Date: 1750 a destructive infectious disease especially of apples, pears, and related fruits caused by a bacterium (Erwinia amylovora) …   New Collegiate Dictionary

  • fire blight — noun a bacterial plant disease that mainly affects apples, pears and some other members of the Rosaceae family …   Wiktionary

  • fire blight — /ˈfaɪə blaɪt/ (say fuyuh bluyt) noun a plant disease which particularly affects pears, apples, quinces, etc., caused by a bacterium, Erwinia amylovora, and causing the blossom, twigs and fruit to wither. Also, fireblight. {from the burnt look of… …   Australian English dictionary

  • blight — blightingly, adv. /bluyt/, n. 1. Plant Pathol. a. the rapid and extensive discoloration, wilting, and death of plant tissues. b. a disease so characterized. 2. any cause of impairment, destruction, ruin, or frustration: Extravagance was the… …   Universalium

  • blight canker — noun a phase of fire blight in which cankers appear • Hypernyms: ↑fire blight, ↑pear blight * * * noun : a phase of fire blight characterized by cankers …   Useful english dictionary


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