Branch death, or flagging, at multiple locations in the crown of a diseased elm. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Ascomycota is a Division / Phylum of Fungi, and subkingdom Dikarya, whose members are commonly known as the Sac Fungi. Pezizomycotina is a subphylum of the Ascomycota (fungi which form their spores in a sac-like ascus) and is more or less synonymous with the older taxon Euascomycota Sordariomycetes is a class of the subdivision Pezizomycotina, which includes ascomycetous fungi.

Dutch elm disease (DED) is a fungal disease of elm trees which is spread by the elm bark beetle. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Elms are Deciduous and Semi-deciduous Trees comprising the genus Ulmus, family Ulmaceae, found A bark beetle is one of approximately 220 Genera with 6000 Species of Beetles in the Subfamily Scolytinae. Although believed to be originally native to Asia, it has been accidentally introduced into America and Europe, where it has devastated native populations of elms which had not had the opportunity to evolve resistance to the disease. The Americas are the lands of the Western hemisphere or New World, consisting of the Continents of North America and South America The name Dutch elm disease refers to the identification of the disease in the 1920s in the Netherlands; the disease is not specific to the Dutch Elm hybrid ^{[1] [2]}

Overview

The causative agents of DED are ascomycete microfungi. The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Although all naturally occurring Field Elm Ulmus minor × Wych Elm U Ascomycota is a Division / Phylum of Fungi, and subkingdom Dikarya, whose members are commonly known as the Sac Fungi. Microfungi are Fungi, Eukaryotic Organisms such as Molds Mildews and rusts which exhibit tube tip-growth and Three species are now recognized: Ophiostoma ulmi, which afflicted Europe in 1910, reaching North America on imported timber in 1928, Ophiostoma himal-ulmi, a species endemic to the western Himalaya, and the extremely virulent species, Ophiostoma novo-ulmi, which was first described in Europe and North America in the 1940s and has devastated elms in both areas since the late 1960s ^[3]. Year 1910 ( MCMX) was a Common year starting on Saturday (link will display calendar of the Gregorian calendar (or a Common year starting The origin of O. novo-ulmi remains unknown but may have arisen as a hybrid between O. ulmi and O. himal-ulmi ^[4] The new species was widely believed to have originated in China, but a comprehensive survey there in 1986 found no trace of it, although elm bark beetles were very common ^[4]. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Year 1986 ( MCMLXXXVI) was a Common year starting on Wednesday (link displays 1986 Gregorian calendar) A bark beetle is one of approximately 220 Genera with 6000 Species of Beetles in the Subfamily Scolytinae.

The disease is spread in North America by two species of bark beetles (Family: Curculionidae, Subfamily: Scolytinae): the native elm bark beetle, Hylurgopinus rufipes, and the European Elm Bark Beetle, Scolytus multistriatus. Curculionidae is the family of the "true" Weevils (or Snout beetles. In Europe, whilst the aforementioned Scolytus multistriatus again acts as vector for infection, it is much less effective than the Large Elm Bark Beetle Scolytus scolytus. In Epidemiology, a vector is an Organism that does not cause Disease itself but which transmits Infection by conveying Pathogens from

In an attempt to block the fungus from spreading further, the tree reacts to the presence of the fungus by plugging its own xylem tissue with gum and tyloses, bladder-like extensions of the xylem cell wall. In Vascular plants xylem is one of the two types of transport tissue Phloem being the other A cell wall is a tough flexible and sometimes fairly rigid layer surrounding a cell, located external to the Cell membrane, which provides the cell with structural As the xylem (one of the two types of vascular tissue produced by the vascular cambium, the other being the phloem), delivers water and nutrients to the rest of the plant, these plugs prevent them from travelling up the trunk of the tree, eventually killing it. This is an article about vascular tissue in plants For transport in animals see Circulatory system. The vascular cambium is a Lateral meristem in the Vascular tissue of plants In Vascular plants phloem is the living tissue that carries organic Nutrients (known as photosynthate particularly Sucrose, a sugar to A tree is a perennial Woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or The first symptom of infection is usually an upper branch of the tree with leaves starting to wither and yellow in summer, months before the normal autumnal leaf shedding. This progressively spreads to the rest of the tree, with further dieback of branches. Eventually, the roots die, starved of nutrients from the leaves. Often, not all the roots die: the roots may put up small suckers. These may grow up for some years into small elm trees, but after a decade or so the new trunks become large enough to support the bark beetles, and with their inevitable arrival the fungus returns, and the new tree dies. ^[3]

Disease range

Europe

Dutch elm disease was first noticed in Europe in 1910, and spread slowly, reaching Britain in 1927. See also Kingdom of Great Britain Great Britain (Breatainn Mhòr Prydain Fawr Breten Veur Graet Breetain is the larger of the two main islands This first strain was a relatively mild one, which only killed a small proportion of elms, more often just killing scattered branches, and had largely died out by 1940. It was isolated in Holland in 1921 by Marie Beatrice Schwarz, a pioneering Dutch phytopathologist, and this discovery would lend the disease its name. [6]

In about 1967, a new, far more virulent strain arrived in Britain on a shipment of Rock Elm logs from North America, and this strain proved both highly contagious and lethal to all of the European native elms; more than 25 million trees died in the UK alone. Ulmus thomasii Sarg the Rock Elm or Cork Elm, is a Deciduous tree native primarily to the Midwestern United By 1990-2000, very few mature elms were left in Britain or much of northern Europe. One of the most distinctive English countryside trees, the English Elm U. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland Ulmus procera Salisb the English Elm or Atinian Elm was before the advent of Dutch elm disease, one of the largest and fastest-growing procera Salisb. (see e. g. John Constable's painting The Hay Wain), is particularly susceptible. John Constable ( 11 June 1776 &ndash 31 March 1837 The Hay Wain is an oil on canvas painting by John Constable. It was finished in 1821 and shows a hay Wain near Flatford Mill Thirty years after the epidemic, these magnificent trees, which often grew to > 45 m high, are long gone. The species still survives in hedgerows, as the roots are not killed and send up root sprouts ("suckers"). A hedge is a line of closely spaced Shrubs and bushes planted and trained in such a way as to form a barrier or to mark the boundary of an area These suckers rarely reach more than 5 m tall before succumbing to a new attack of the fungus. However, established hedges kept low by clipping have remained apparently healthy throughout the nearly 40 years since the onset of the disease in the UK.

Sign on A27, Brighton

The largest concentration of mature elm trees remaining in England is in Brighton & Hove, East Sussex, where 15,000 elms still stand (2005 figures), several of which are estimated to be over 400 years old. Council and directorates The leader of the council is Conservative Mary Mears East Sussex is a county in South East England. It is bordered by the counties of Kent, Surrey and West Sussex, and to the Their survival is owing to the isolation of the area, between the English Channel and the South Downs, and the assiduous efforts of local authorities to identify and remove infected sections of trees immediately when they show signs of the disease. The South Downs is one of the four areas of Chalk Downland in southern England. Empowered by the Dutch Elm Disease (Restriction on Movement of Elms) (Amendment) Order 1988 [7], local authorities may order the destruction of any infected trees or timber, although in practice they usually do it themselves, successfully reducing the numbers of elm bark beetle Scolytus spp, the vector of Elm Disease. [8]

United States

Certified arborist removing infected elm in Saint Paul, Minnesota. Saint Paul ( abbreviated St Paul) is the capital and second most populous city in the U

The disease was first reported in the United States in 1928, with the beetles believed to have arrived in a shipment of logs from the Netherlands destined for use as veneer in the Ohio furniture industry. The United States of America —commonly referred to as the The Netherlands ( Dutch:, ˈnedərlɑnt is the European part of the Kingdom of the Netherlands, which consists of the Netherlands the Netherlands Ohio ( is a Midwestern state of the United States. As part of the Great Lakes region, Ohio has long been a cultural and geographical crossroads Furniture is the Mass noun for the movable objects which may support the human body (seating furniture and beds, provide storage or hold objects on horizontal The disease spread slowly from New England westward and southward, almost completely destroying the famous Elms in the 'Elm City' of New Haven, reaching the Detroit area in 1950[9], the Chicago area by 1960, and Minneapolis by 1970. History See also History of New England New England's earliest inhabitants were Algonquian -speaking Native Americans including the Chicago (ʃɪˈkɑːgoʊ is the largest City by population in the state of Illinois and the American Midwest of the United States.

Canada

Dutch elm disease reached Eastern Canada during the Second World War, and spread to Ontario in 1967, Manitoba in 1975 and Saskatchewan in 1981. Ontario (ɒnˈtɛrioʊ is a province located in the central part of Canada, the largest by population and second largest after Quebec Year 1967 ( MCMLXVII) was a Common year starting on Sunday (link will display full calendar of the 1967 Gregorian calendar. Manitoba (English ˌmænɨˈtoʊbə French /manitoba/ is a province of Canada, spanning 647797 square kilometres (250116  sq mi of North America Year 1975 ( MCMLXXV) was a Common year starting on Wednesday (link will display full calendar of the Gregorian calendar. Saskatchewan (səˈskætʃəwən) is a prairie province in Canada, which has an area of 588276 Year 1981 ( MCMLXXXI) was a Common year starting on Thursday (link displays the 1981 The largest American, or American White, Elm Ulmus americana known to exist in Ontario, the Sauble Elm, succumbed to the disease and was cut down in September of 1968 [10]. Ulmus americana, generally known as the American Elm or less commonly as the White Elm or Water Elm, is a species native to eastern Ontario (ɒnˈtɛrioʊ is a province located in the central part of Canada, the largest by population and second largest after Quebec In Toronto, Ontario, 80% of the elm trees have been lost to Dutch elm disease, and many more have fallen victim to the disease in Ottawa, Montreal and other cities during the 1970s and 1980s. Toronto (təˈrɒntoʊ colloquially pronounced or) is the largest city in Canada and is the provincial capital of Ontario Ottawa (ˈɒtəwə or sometimes /ˈɒtəwɑː/ is the Capital of Canada and the country's fourth largest municipality. Montreal, or Montréal in French ( pronounced in French, in English) is the largest city in the Canadian province of Quebec Alberta and British Columbia are the only provinces that are currently free of Dutch elm disease, although an elm tree in southeastern Alberta was found diseased in 1998 and was immediately destroyed before the disease could spread any further. Alberta (ælˈbɝtə is one of Canada's prairie provinces. It became a province on September 1 1905 British Columbia (ˌbrɪtɨʃ kəˈlʌmbiə ( BC) ( (la Colombie-Britannique C Alberta (ælˈbɝtə is one of Canada's prairie provinces. It became a province on September 1 1905 Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Thus, this was an isolated case. Today, Alberta has the largest number of elms unaffected by Dutch elm disease in the world. Alberta (ælˈbɝtə is one of Canada's prairie provinces. It became a province on September 1 1905 Aggressive measures are being taken to prevent the spread of the disease into Alberta as well as further progression of the disease in other parts of Canada. The City of Edmonton has banned elm pruning from March 31 to October 1, since fresh pruning wounds will attract the beetles during the warmer months. Edmonton (ˈɛdmɨntɨn is the capital of the Canadian province of Alberta.

Practical Information for the Elm tree owner: DED is caused by a fungus. A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ It is primarily spread 3 ways: 1) by beetle vectors which carry the fungus from tree to tree (the beetle doesn't kill the tree, the fungus it carries does). In Epidemiology, a vector is an Organism that does not cause Disease itself but which transmits Infection by conveying Pathogens from 2) through direct contact of an infected tree's roots with a neighboring healthy tree. 3) by pruning of a healthy tree with saws which have been used to take down diseased trees. This third method of spread is common and not recognized by many tree pruning and removal services. Arborists at Kansas State University claim that cleaning blades with a 10% solution of a household bleach will prevent this type of spread. Owners of healthy trees should be vigilant about the companies they hire to prune healthy trees. Be certain blades are disinfected between use to remove dead trees and use to prune healthy trees.

Treatment

The first fungicide used for preventive treatment of Dutch elm disease was Lignasan BLP (carbendazim phosphate), which was introduced in the 1970s. Carbendazim is a widely used broad-spectrum Benzimidazole fungicide. This had to be injected into the base of the tree using specialized equipment, and was never especially effective. It is still sold under the name "Elm Fungicide". Arbotect (thiabendazole hypophosphite) became available some years later, and it has been proven effective. Thiabendazole ( TBZ or tiabendazole) is a Fungicide and parasiticide. Arbotect must be injected every 2 to 3 years to provide ongoing control; the disease generally cannot be eradicated once a tree is infected.

Alamo (propiconazole) has become available more recently and shows some promise, though several university studies show it to be less effective than Arbotect treatments. Propiconazole is a Triazole Fungicide used agriculturally on grasses grown for seed mushrooms corn wild rice peanuts almonds sorghum oats pecans apricots Alamo is primarily recommended for treatment of Oak Wilt. Oak wilt is a Fungal Disease which can quickly kill an Oak tree

Treatment of diseased trees is costly and at best will prolong the life of the tree by perhaps five or ten years. It is usually only justified when a tree has unusual symbolic value or occupies a particularly important place in the landscape.

Resistant trees

Research to select resistant cultivars and varieties began in the Netherlands in 1928, and in the USA since the disease became endemic there. Initial efforts in the Netherlands involved crossing varieties of U. minor and U. glabra, but later included the Himalayan or Kashmir Elm U. wallichiana as a source of anti-fungal genes. Early efforts in the USA involved the hybridization of the Siberian Elm Ulmus pumila with the American Elm, and produced a resistant tree, but that lacked the beauty, traditional shape, and landscape value of the American Elm; few were planted. Ulmus pumila L the Siberian Elm, is native to Turkestan, eastern Siberia, Mongolia, Xizang ( Tibet

Recent research in Sweden has established that early-flushing clones are less susceptible to DED owing to an asynchrony between DED susceptibility and infection ^[5]. "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation.

Cultivars

Resistant American Elm cultivars are commercially available in North America, notably:

• 'Princeton', a cultivar selected in 1922 by Princeton Nurseries for its landscape merit. The Princeton Elm is a cultivar of the American Elm Ulmus americana originally selected in 1920 by a New Jersey grower for its landscape qualities Year 1922 ( MCMXXII) was a Common year starting on Sunday of the Gregorian calendar. By happy coincidence, this cultivar was revealed to be highly resistant in inoculation studies carried out by the USDA in the early 1990s. Because mature trees planted in the 1920s still survive, the properties of the mature plant are well known.
• 'Valley Forge', has demonstrated resistance to Dutch elm disease approximately equal to that of the Princeton Elm cultivar in controlled USDA tests. The American Elm Ulmus americana cultivar ' Valley Forge' was raised by the Maryland Agricultural Research Service and released to wholesale nurseries by
• 'Lewis & Clark' (Prairie Expedition TM ), the latest cultivar to be released in 2004, cloned from a tree found growing in North Dakota that had survived unscathed when all around had succumbed to disease. The American Elm Ulmus americana cultivar ' Lewis & Clark' ( Prairie Expedition™) is a new development from the North Dakota State University "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " North Dakota ( is a state located in the Midwestern and Western regions of the United States of America.

There is also the 'American Liberty', in fact a set of six cultivars of moderate to high resistance produced through selection over several generations starting in the 1970s. The American Elm Ulmus americana cultivar ' American Liberty' is in fact a group of six genetically distinct cultivars under a single name although they are superficially Marketed as a single variety, nurseries selling the "Liberty Elm" actually distribute the six cultivars at random and thus, unfortunately, the resistance of any particular tree cannot be known. One of the cultivars Independence' is covered by patent (U. The American Elm Ulmus americana cultivar ' Independence' was raised by Eugene B S. Plant Patent 6227).

In 2007, the Elm Recovery Project from the University of Guelph in Ontario, Canada reported that cuttings from healthy surviving old elms surveyed across Ontario had been grown to produce a bank of resistant trees, isolated for selective breeding of highly resistant cultivars [11] .

The Slippery or Red Elm U. The Slippery Elm ( Ulmus rubra) is a Species of Elm native to eastern North America (from southeast North Dakota, east to southern rubra, that overlaps the range of the American Elm, is less susceptible to Dutch elm disease than many elms, but this quality seems to have somehow largely evaded the attention of the resistance programme.

Even resistant cultivars can become infected, particularly if the tree is under stress from drought and other environmental conditions, and if the disease pressure is high. With the exception of the Princeton Elm, no trees have yet been grown to maturity. The oldest Liberty Elm was planted in about 1980, and the trees cannot be said to be mature until they have reached an age of sixty years.

In 2001, English Elm U. Ulmus procera Salisb the English Elm or Atinian Elm was before the advent of Dutch elm disease, one of the largest and fastest-growing procera was genetically engineered to resist disease, in experiments at Abertay University, Dundee, Scotland, by transferring anti-fungal genes into the elm genome using minute DNA-coated ball bearings [12]. Dundee (Dùn Dèagh is the fourth-largest city in Scotland and fully named as Dundee City, one of Scotland's 32 local government council Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. However, there are no plans to release the trees into the countryside.

Hybrid cultivars

There have been many attempts to breed disease resistant cultivar hybrids and they have usually involved a genetic contribution from Asian elm species which have demonstrable resistance to this fungal disease. Much of the early work in Europe was undertaken in the Netherlands. The Dutch research programme ended after 64 years in 1992. Year 1992 ( MCMXCII) was a Leap year starting on Wednesday (link will display full 1992 Gregorian calendar) The programme had two major successes: 'Columella' and 'Nanguen' (Lutèce) ^[6], both found to be actually immune to the disease when inoculated with unnaturally high doses of the fungus. A Dutch Cultivar raised by the Dorschkamp Research Institute in Wageningen, ' Columella' was derived from a selfed seedling of the hybrid 'Plantyn' One of the last Dutch hybrid cultivars to be released ' Nanguen' ( Lutèce™) is a complex fourth generation tree with an ancestry comprising four Field The patent for the Lutèce clone was purchased by the French Institut National de la Recherche Agronomique (INRA), which subjected the tree to 20 years of field trials in the Bois de Vincennes, Paris, before releasing it for sale in 2002. The Bois de Vincennes is a park in the English landscape manner to the east of Paris. Paris (ˈpærɨs in English; in French) is the Capital of France and the country's largest city See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar.

In Italy, research is continuing at the Istituto per la Protezione delle Piante, Florence, to produce a wide range of disease-resistant trees using a variety of Asiatic species crossed with the early Dutch hybrid Plantyn (elm hybrid) as a safeguard against any future mutation of the disease ^[7]. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest ' Plantyn' (Anglicized form of Plantijn was one of three Dutch hybrid Elms released in 1973. Four trees with very high levels of resistance; 'San Zanobi' and 'Plinio' ^[8] were released in 2003, followed four years later by 'Arno' and 'Fiorente'. ' San Zanobi' is an Elm Cultivar raised by the Istituto per la Protezione delle Piante (IPP Florence. ' Plinio' is an Elm Cultivar derived from a crossing of the Dutch hybrid cultivar 'Plantyn' with the Siberian Elm Ulmus Year 2003 ( MMIII) was a Common year starting on Wednesday of the Gregorian calendar. ' Arno' is a Cultivar derived from a crossing of the Dutch hybrid cultivar 'Plantyn' with the Siberian Elm Ulmus pumila ' Fiorente' is an Elm Cultivar derived from a crossing of the Siberian Elm Ulmus pumila clone S All four feature the Siberian Elm Ulmus pumila as a source of disease-resistance genes. Ulmus pumila L the Siberian Elm, is native to Turkestan, eastern Siberia, Mongolia, Xizang ( Tibet

The European White Elm

There is also the unique example of the European White Elm U. Ulmus laevis Pall the European White Elm, yclept Fluttering Elm Spreading Elm and in the USA, Russian Elm, is a laevis which has little innate resistance to Dutch elm disease but is eschewed by the vector bark beetles and only rarely becomes infected. Recent research has indicated that it is the presence of certain organic compounds, such as triterpenes and sterols, which serves to make the tree bark unattractive to the beetle species that spread the disease ^[9]. Terpenes are a large and varied class of Hydrocarbons, produced primarily by a wide variety of plants particularly Conifers though also by some insects such Sterols, or steroid alcohols are a subgroup of Steroids with a Hydroxyl group at the 3-position of the A-ring

Possible earlier occurrences

A less devastating form of the disease, caused by a different fungus, had possibly been present in Britain for some time, as this passage in Richard Jefferies' 1883 book, Nature near London, shows:

There is something wrong with elm trees. John Richard Jefferies ( 6 November 1848 - 14 August 1887) was an English nature writer noted for his depiction of English rural In the early part of this summer, not long after the leaves were fairly out upon them, here and there a branch appeared as if it had been touched with red-hot iron and burnt up, all the leaves withered and browned on the boughs. First one tree was thus affected, then another, then a third, till, looking round the fields, it seemed as if every fourth or fifth tree had thus been burnt. [. . . ] Upon mentioning this I found that it had been noticed in elm avenues and groups a hundred miles distant, so that it is not a local circumstance.

This suggestion remains largely speculative, and there is no proof that it was caused by a fungus related to Dutch elm disease.

From analysis of pollen in peat samples, it is apparent the elm all but disappeared from Europe during the mid-Holocene period about 6000 years ago. Examination of sub-fossil elm wood has suggested that Dutch elm disease may have been responsible [13].

References

External links

• Elm Recovery Project - Guelph University (Canada)
• Dutch elm disease - info from the Government of Alberta
• Dutch elm disease - info from the Government of British Columbia
• DED info from Rainbow Treecare Scientific Advancements
• The Mid-Holocene Ulmus decline: a new way to evaluate the pathogen hypothesis