Saw this today about sudden apple decline on my ID listserve.
Original article from:
https://www.growingmagazine.com/education/rapid-apple-decline-psu-remains-mystery/
Other links on topic at end of post.
PRO/PL> Undiagnosed sudden decline, apple - USA
(promed@promedmail.org)
Date: Fri, 29 Dec 2017 03:02:35 +0000
From: promed@promedmail.org
Subject: PRO/PL> Undiagnosed sudden decline, apple - USA
To: promed-post@promedmail.org, promed-plant-post@promedmail.org
UNDIAGNOSED SUDDEN DECLINE, APPLE - USA
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A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Mon 25 Dec 2017
Source: Growing [edited]
<https://www.growingmagazine.com/education/rapid-apple-decline-psu-remains-mystery/>
In the Northeast [of the US], Canada and North Carolina, young dwarf trees in high-density orchards are dying [see ProMED-mail post http://promedmail.org/post/20100608.1911] with increased frequency.
The Pennsylvania Department of Agriculture, Cornell University, University of North Carolina and others have teamed up to solve the mystery of Rapid (or Sudden) Apple Decline (RAD or SAD).
There seems to be some connection to M9 rootstock, although other rootstocks also can be impacted. Fuji, Gala and Golden Delicious cultivars appear most susceptible. This might indicate some cultivar-rootstock combination triggering RAD. Observations do not point to any specific pathogen, abiotic factors may play a role, [but] there is no obvious common denominator among the impacted trees.
Trees, even those full of fruit, quickly die from RAD. The graft union shows necrosis [which] continues up the bark. Severe bark shedding near the graft union [and] cankers are also seen. Within 2 to 3 weeks, leaves turn yellow and the tree dies. There are few signals that anything is wrong prior to the sudden emergence of symptoms. Trees collapse completely, despite the wood being solid and the roots healthy. In any given block, trees with RAD are scattered with no pattern, [and] some trees can remain healthy.
Because stress is believed to be a factor in RAD, growers are advised to eliminate as many stressors as possible. Alternative rootstocks to
M9 could afford protection. Other [factors] may be playing some role in the syndrome and viruses or [other] pathogens - known or as yet unidentified - may also be contributing.
[Byline: Tamara Scully]
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[This undiagnosed disease or disorder in apple orchards was previously reported from Michigan and New York (ProMED-mail post http://promedmail.org/post/20100608.1911). It now appears to be much more widely distributed but unfortunately not much progress seems to have been made in the search for a cause.
Association with specific dwarfing rootstocks and apple varieties may imply graft transmissible agents such as viruses, viroids or phytoplasmas. Molecular methods are needed for their detection, but no information is provided in the report above whether a systematic molecular search for any pathogens has already been undertaken. As mentioned above, SAD may also represent a syndrome including a number of different factors, which would make the task of identifying a cause much more complex.
Generally, to identify a biotic or abiotic cause for a disease or disorder of unknown aetiology, a defined process must be followed:
description of specific symptoms in individual plants; patterns of their distribution in space and time; evidence for or against transmission of symptoms and spread of the condition; Koch's rules (i.e. to re-isolate an infectious pathogen after culture and transmission, or equivalent process for non-culturable pathogens) to test for causation by a biotic agent; molecular studies to identify a known or characterise a novel potential infectious agent. Especially in slow growing hosts, such as trees, this process may take many years and it would be complicated considerably if a previously unknown pathogen were to be involved.
Maps
USA:
<http://www.mapsofworld.com/usa/usa-state-and-capital-map.html>
Individual states via:
<http://www.mapsofworld.com/usa/states/>
Pictures
SAD symptoms:
<http://www.goodfruit.com/wp-content/uploads/rapidAppleDecline1010442-1-1-620x465.jpg>,
<https://www.agprofessional.com/sites/default/files/image_galleryzoom_1.jpg>,
<http://www.omafra.gov.on.ca/english/crops/hort/news/orchnews/2016/on-1216a6f3.jpg>,
<http://www.goodfruit.com/wp-content/uploads/rapidAppleDecline1010428-2-620x727.jpg>,
<http://www.mpnnow.com/storyimage/NU/20171211/NEWS/171219934/AR/0/AR-171219934.jpg>
and
<http://files.growingproduce.com/growingproduce/wp-content/uploads/2017/08/tree-decline-new-york.jpg>
Links
Additional news stories:
<http://www.freshplaza.com/article/186470/New-York-state-experts-probe-sudden-apple-decline>,
<http://www.mpnnow.com/news/20171211/experts-probe-sudden-apple-decline>,
<https://www.agprofessional.com/article/rapid-apple-decline-hits-trees-northeast>,
<http://www.goodfruit.com/whats-killing-these-trees/> and <http://www.lancasterfarming.com/farming/produce/mystery-issue-killing-apple-trees/article_fd8cbacf-57fc-5af8-9a4f-486faca643f6.html>
Information on SAD:
<https://extension.psu.edu/rapid-apple-decline-rad-or-sudden-apple-decline-sad>,
<http://www.omafra.gov.on.ca/english/crops/hort/news/orchnews/2016/on-1216a6.htm>,
<http://www.hort.cornell.edu/expo/proceedings/2017/TreeFruitPestMGMT.AppleTrunkDisorders.Rosenberger.2017.pdf>
and
<http://www.growingproduce.com/fruits/apples-pears/new-york-growers-input-needed-on-tree-decline/>
Information on apple rootstocks, including M9:
<http://www.gardenaction.co.uk/fruit_veg_diary/fruit_veg_mini_project_september_2a_apple.asp>.
- Mod.DHA]
[See Also:
Crown & root rot, apple - USA: (eastern)
http://promedmail.org/post/20170821.5263568
2016
----
Fireblight, apple - Canada: (QC)
http://promedmail.org/post/20160919.4500366
2014
----
Fireblight, apple - Canada: (NS)
http://promedmail.org/post/20140908.2756240
2013
----
Apple proliferation phytoplasma- N America: 1st report, Canada
http://promedmail.org/post/20130415.1646164
2012
----
Fungal diseases, apple - USA: (NY, MI)
http://promedmail.org/post/20120906.1282861
2010
----
Undiagnosed mould & scab, apple - Mexico (QE)
http://promedmail.org/post/20100822.2939
Undiagnosed disease, apple - USA: (MI, NY)
http://promedmail.org/post/20100608.1911
and additional items on apple diseases in the archives] .................................................sb/dha/ec/lm
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