Editing Dutch elm disease (section)

== Overview ==
[[File:David Elm with DED 2.jpg|thumb|Branch death, or flagging, at multiple locations in the [[crown (botany)|crown]] of a diseased elm]]
Dutch elm disease (DED) is caused by [[ascomycete]] [[microfungi]].<ref name=ASCoverview>[http://hhh.gavilan.edu/rmorales/documents/Botanych.14fungiascomycete_001.ppt Ascomycetes: Phylum Ascomycota], ''Biology of Plants, Seventh Edition'', W. H. Freeman and Company, 2005.</ref> Three species are now recognized:
* ''[[Ophiostoma ulmi]]'', which afflicted Europe from 1910, reaching North America on imported timber in 1928.<ref name = "DED1936paper">[https://archive.org/details/dutchelmdiseaseg00clin/page/n3 Clinton, G. P., McCormick, Florence A., ''Dutch elm disease, Graphium ulmi''; New Haven, 1936]</ref>
* ''[[Ophiostoma himal-ulmi]]'',<ref>{{cite journal |last1=M.D.  |title=''Ophiostoma himal-ulmi'' sp. nov., a new species of Dutch elm disease fungus endemic to the Himalayas |journal=Mycological Research |volume=99 |issue=2 |pages=205–215 |year=1995 |issn=0953-7562 |doi=10.1016/S0953-7562(09)80887-3 |first1=C.M. |last2=Mehrotra |first2=M.D. }}</ref> a species endemic to the western [[Himalaya]].
* ''[[Ophiostoma novo-ulmi]]'', an extremely virulent species from Japan which was first described in Europe and North America in the 1940s and has devastated elms in both continents since the late 1960s.<ref name=Spooner>{{cite book |first1=Brian |last1=Spooner |first2=Peter |last2=Roberts |title=Fungi |series=Collins New Naturalist Library |volume=96 |url=https://books.google.com/books?id=JNL6Lmo-gkYC&pg=PT235 |year=2010 |publisher=HarperCollins |isbn=978-0-00-740605-0 |page=235 |orig-year=2005}}</ref><ref name=Johnson>Johnson, O. (2011). ''Champion Trees of Britain and Ireland''. Royal Botanic Gardens, Kew.
{{ISBN|978-1842464526}}</ref>

[[File:RN Beetle galleries, Wych elm.JPG|thumb|Beetle feeding galleries on [[wych elm]] trunk]]
[[File:Dutch Elm Disease affecting a mature English Elm at Wst Point, NY June 2010.jpg|thumb|right|An infected English elm at West Point, NY, July 2010]]

DED is spread in North America by three species of bark beetles (Family: [[Curculionidae]], Subfamily: Scolytinae):
* The native elm bark beetle, ''[[Hylurgopinus rufipes]]''.
* The smaller European elm bark beetle, ''[[Scolytus multistriatus]]''.
* The banded elm bark beetle, ''[[Scolytus schevyrewi]]''.

In Europe, while ''S. multistriatus'' still acts as a [[Vector (epidemiology)|vector]] for infection, it is much less effective than the large elm bark beetle, ''[[Scolytus scolytus|S. scolytus]]''. ''H. rufipes'' can be a vector for the disease, but is inefficient compared to the other vectors. ''S. schevyrewi'' was found in 2003 in [[Colorado]] and [[Utah]].{{cn|date=May 2025}}

Other reported DED vectors include ''Scolytus sulcifrons'', ''S. pygmaeus'', ''S. laevis'', ''Pteleobius vittatus'' and ''Р. kraatzi''.<ref name="Izhevsky2005">{{cite book|last1=Ижевский|first1=С.С.|last2= Никитский|first2=Н.Б.|last3= Волков|first3= О.Г.|last4=Долгин|first4=М.М|title= Иллюстрированный справочник. жуков-ксилофагов – вредителей леса и лесоматериалов Российской Федерации|date=2005|location= Тула|publisher= Российская Академия Наук, Уральское отделение, Коми научный центр, Институт биологии. (Izhevsky, SS; et al. (2005). "An illustrated guide to the xylophagous beetles injuring forests and timber in the Russian Federation". Russian Academy of Sciences, Ural Branch, Komi Science Center, Institute of Biology. Tula)|pages=165|url=http://herba.msu.ru/shipunov/school/books/izhevskij2005_ill_sprav_zhukov-ksilofagov.pdf}}</ref> Other elm bark beetle species are also likely vectors.

===Field resistance===
'Field resistance' is an umbrella term covering the various factors by which some elms avoid infection in the first place, rather than survive it. A clear example would be the [[Ulmus laevis|European White Elm]] (''Ulmus laevis'') which, while having little or no genetic resistance to DED, synthesizes a [[triterpene]], Alnulin, rendering the bark distasteful to the vector beetles, obliging them to look further afield for more suitable elms. Another would be the inability of the beetles to see elms which did not break the silhouette. 'Weeping' elms are often spared infection owing to the beetles' aversion to hanging upside-down while feeding.

===Mechanism===
In an attempt to block the fungus from spreading farther, the tree reacts by plugging its own [[xylem|xylem tissue]] with gum and [[Tylosis (botany)|tyloses]], bladder-like extensions of the xylem [[cell wall]]. 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]], starving the tree of water and nutrients, which eventually kills it.

===Symptoms===
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 morbidity spreads in a progressive manner throughout 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 of some species, especially the [[Ulmus minor 'Atinia'|English elm]] (formerly ''Ulmus procera''), can repeatedly put up suckers, which flourish for approximately 15 years before dying off.<ref name="Spooner"/>