Fire blight, also written fireblight, is a contagious disease affecting apples, pears, and some other members of the family Rosaceae.

Pears are the most susceptible, but apples, loquat, crabapples, quinces, hawthorn, cotoneaster, Pyracantha, raspberry and some other rosaceous plants are also vulnerable.

[3] In Europe it is listed as a quarantine disease, and has been spreading along hawthorn (Crataegus) hedges planted alongside railways, motorways and main roads.

Today, E. amylovora can currently be found in all the provinces of Canada, as well as in some parts of the United States of America, including Alabama, California, Colorado, Connecticut, Georgia, Illinois, Maine, Maryland, Massachusetts, Michigan, New York, North Carolina, Ohio, Oregon, Pennsylvania, Texas, Utah, Virginia, Washington, West Virginia and Wisconsin.

[citation needed] It is believed that the pathogen was first introduced into Northern Europe in the 1950s through fruit containers, contaminated with bacterial ooze, imported from the USA.

A few minutes of heavy hail can spread the disease throughout an entire orchard and growers normally do not wait until symptoms appear but begin control measures[citation needed] within a few hours.

[citation needed] Once the bacterium gains access to the xylem or cortical parenchyma of the plant, it causes blackened, necrotic lesions, which may also produce a viscous exudate.

[citation needed] Unfortunately, while chemicals and meticulous pruning can keep an infected tree productive, there is no known comprehensive cure for fire blight; the best that can be done is to prevent its spread by measures such as avoidance of overhead water systems, as falling water can spread the disease and the careful pruning of tainted stems or branches.

However, some essential factors of pathogenicity are variations in the synthesis of extracellular polysaccharides (EPS) and the mechanism of type III secretion system and its associated proteins.

[11] EPS helps bacterial pathogens avoid plant defenses, “clog” the host’s vascular system, protect bacteria against desiccation and attach to both surfaces and one another.

[citation needed] Tissues affected by the symptoms of Erwinia amylovora include blossoms, fruits, shoots, and branches of apple (Pomoideae), pear, and many other rosaceous plants.

[13] This results in a dull, gray-green appearance 1–2 weeks after petal fall, and eventually tissues will shrivel and turn black.

Certain biological controls consisting of beneficial bacteria or yeast can also prevent fire blight from infecting new trees.

[17] Methods to predict the likelihood of an outbreak so that control measures can be best targeted, were introduced from the 1980s following the work of Eve Billings at East Malling Research Station, UK.

[20] New research conducted by John C. Wise out of Michigan State University shows that E. amylovora can be controlled with relative efficacy through tree trunk injection of either streptomycin, potassium phosphites (PH), or acibenzolar-S-methyl (ASM).

High risk countries are encouraged not to import plants susceptible to the pathogen into their territory because, once the bacteria become established in an area it is nearly impossible to eradicate the disease.

Imported and infected crops are destroyed as soon as they are noticed since the bacteria spreads very rapidly and eradication methods are usually costly and inefficient.

[citation needed] Current fire blight strategies depend upon phytosanitary measures to lessen inoculum in the plantation and the utilization of splash medicines to forestall contamination, particularly blossom infections.

Decreasing essential inoculum in the plantation by removing remainder holdover cankers during winter pruning is a set up as a basic method of control fire blight disease.

[23] Prohexadione calcium (BASF brand name Apogee in the United States) is a plant growth inhibitor which is recommended for shoot blight.

[24] Besides the historical significance of being the first bacterium proven to be a plant pathogen, fire blight is extremely important economically.

[26] In southern Germany apple and pear trees have been a part of the landscape for a long time, and are difficult to protect.

Food sellers and shoppers prize these cultivars for their appearance, quality, flavour, and storability, while cultivators additionally esteem their orchard attributes and guaranteed market due to this popularity.

To maintain the desirable qualities of a cultivar while at the same time changing its disease resistance through ordinary breeding techniques is for all intents and purposes impossible due to the apple's heterozygosity, self-incongruence, and long growth span.