Editing Dutch elm disease (section)

==Preventive treatment==

===Mechanical===
[[File:Ringbarked elm, The Meadows - geograph.org.uk - 958758.jpg|thumb|right|Diseased elm [[ringbarked]] to slow down transmission before felling.]]The first attempts to control Dutch elm disease consisted of pruning trees to remove and burn diseased [[timber]]. While this method was effective in [[New York State]] and adjacent areas, its cost made it uneconomical except in large cities where elms were considered valuable attractions.

===Chemical===
In the US, when Dutch elm disease spread away from the Atlantic coast, control focused on controlling the bark beetle by using [[insecticide]]s such as [[DDT]] and [[dieldrin]], which were sprayed heavily across all parts of elm trees, usually twice a year in the spring and again at a lower concentration in the summer. In its early years, it was generally thought by observers that pesticides did slow the spread of the disease across the United States<ref name="effects">{{cite journal |last=Benton |first=Allen H. |title=Effects on Wildlife of DDT Used for Control of Dutch Elm Disease |journal=[[The Journal of Wildlife Management]] |volume=15 |issue=1 |pages=20–7 |date=January 1951 |doi=10.2307/3796765 |jstor=3796765 }}</ref> but as early as 1947, concern was raised that many bird species were killed in large numbers by ingesting poisoned invertebrates.<ref name="effects"/><ref>{{cite book |first=Dave |last=Dempsey |title=Ruin & Recovery: Michigan's Rise as a Conservation Leader |url=https://books.google.com/books?id=Rwte23t8498C&pg=PA126 |year=2001 |publisher=University of Michigan Press |isbn=978-0-472-06779-4 |page=126}}</ref> In areas sprayed during the 1950s, local people observed birds such as the [[American woodcock]], [[American robin]], [[white-breasted nuthatch]], [[brown creeper]] and various ''[[Poecile]]'' species dying. Biologist [[Rachel Carson]] consequently argued for improved sanitation and against spraying elms, which she saw as having been more effective in areas with earlier and greater experience countering Dutch elm disease.<ref>{{cite book |last=Carson |first=Rachel |author-link=Rachel Carson |title=Silent Spring |isbn=978-0-618-24906-0 |pages=[https://archive.org/details/silentspring00cars_1/page/105 105–115] |title-link=Silent Spring |year=2002 |publisher=Houghton Mifflin Harcourt }}</ref> Spraying against elm bark beetles declined very rapidly after 1962, a trend aided by [[fungicides]].<ref>{{cite journal |title=New Fungicide Fights Dutch Elm Disease |journal=[[Chem. Eng. News]] |volume=42 |issue=37 |pages=29–31 |year=1964 |doi=10.1021/cen-v042n037.p029 }}</ref>

Lignasan BLP ([[carbendazim phosphate]]), introduced in the 1970s, was the first fungicide used to control Dutch elm disease. 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. Arbotect must be injected every two to three years to provide ongoing control; the disease generally cannot be eradicated once a tree is infected. Arbotect is not effective on root graft infections from adjacent elm trees.  It is more than 99.5% effective for three years from beetle infections, which is the primary mode of tree infection.

Alamo ([[propiconazole]]) has become available more recently, though several university studies show it to be effective only for the current season in which it is injected.  Alamo is primarily recommended for treatment of [[oak wilt]].

[[Multistriatin]] is a [[pheromone]] produced by female elm bark beetles, which can be produced synthetically. It has potential in being used to trap male beetles, which carry the fungus.

===Biological===
Because of the ban on the use of chemicals on street and park trees in the Netherlands, the [[University of Amsterdam]] developed a biological vaccine by the late 1980s. Dutch Trig is nontoxic, consisting of a suspension in distilled water of spores of a strain of the fungus ''[[Verticillium albo-atrum]]'' that has lost much of its pathogenic capabilities, injected in the elm in spring. The strain is believed to have enough pathogenicity left to induce an immune response in the elm, protecting it against DED during one growing season. This is called [[induced resistance]].<ref>[http://www.dutchtrig.com/about_dutch_trig/about_dutch_trig.html About Dutch Trig®] {{webarchive|url=https://web.archive.org/web/20101117184339/http://www.dutchtrig.com/about_dutch_trig/about_dutch_trig.html |date=2010-11-17 }}</ref> Trials with the American elm have been successful; in a six-year experiment with the American elm in Denver, CO, annual Dutch elm disease losses declined significantly after the first year from 7 percent to between 0.4 and 0.6 percent;<ref name=Rumbolt09/> a greater and more rapid reduction in disease incidence than the accompanying tree sanitation and plant health care programs.<ref>{{cite web |url=http://www.dutchtrig.com/united_states/denver.html |title=Dutch Trig - United States - Distributors |access-date=2013-08-05 |url-status=dead |archive-url=https://web.archive.org/web/20130615004749/http://www.dutchtrig.com/united_states/denver.html |archive-date=2013-06-15 }}</ref>

Preventive treatment is usually justified only when a tree has unusual symbolic value or occupies a particularly important place in the landscape.