Published Date: 2008-05-20 23:00:33
Subject: PRO/PL> Huanglongbing, citrus - Bhutan: (Chukha)
Archive Number: 20080520.1676

HUANGLONGBING, CITRUS - BHUTAN: (CHUKHA)
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Date: 20 May 2008
Source: Bhutan Today [edited]
<http://bhutantodays.blogspot.com/2008/05/orange-production-falls-in-pachutar-in.html>



Orange production falls in Pachutar in Phuentsholing
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Farmers of Pachutar village in Phuentsholing [Chukha district] are
facing a dilemma. Their orange production has been falling every
year. They have been advised to replace the old trees with new
saplings but this means they have to forego the income from the sale
of oranges for over 5 years untill the new trees start bearing fruit.

The production during the last season was the lowest so far.
Agricultural officials said the trees were more than 20 years old and
have not been managed properly. They said the trees were also stuck
by citrus green[ing], a disease which results in poor flowering and
yellowing of leaves. They said the only answer is to replace the old
trees with new saplings.

The Agriculture Ministry is willing to provide disease resistant
saplings to the people. But the farmers said they are reluctant to
start all over again. Orange trees normally take about 5 years to
start bearing fruit. They said they cannot afford to forego the
income for such a long time as it is the only source of income for
many farmers.

[Byline: Ariya]

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Communicated by:
ProMED-mail
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[Huanglongbing (HLB), or citrus greening, is caused in Asia by the
fastidious phloem-inhabiting bacterium _Candidatus_ Liberibacter
asiaticus, which occurs throughout much of Asia and in parts of the
Americas. Its vector is the Asian citrus psyllid (_Diaphorina
citri_), but it is also often spread by grafting and possibly seed
transmission. The disease is restricted to _Citrus_ and close
relatives because of the narrow host range of the vector. Two other
strains of the pathogen -- _Ca._ L. africanus (including a subsp.
capensis) and _Ca._ L. americanus -- and their specific vectors exist
in the respective areas. Citrus greening has not been reported from
the Mediterranean region or Australia.

HLB is one of the most damaging diseases of citrus crops affecting
leaves and fruits. Symptoms include blotchy mottling and yellowing of
leaves and small, irregularly shaped fruits with a thick, pale peel
and bad taste. Early symptoms may be confused with nutrient
deficiencies. Affected trees become stunted, bear multiple off-season
flowers and may live for only a few years without ever bearing usable
fruit. Disease management requires an integrated approach including
use of clean planting and grafting stock, elimination of inoculum,
use of pesticides for vector control in orchards, and biological
control of vectors in non-crop reservoirs. Biological control by
interplanting of guava is being trialled (see previous ProMED-mail
post no. 20070912.3018).

HLB was reported for the first time in Bhutan in 2003 as being
established in the Punaka and Wangdue districts. The report above
provides evidence that it has spread considerably from there since
Chukha is not immediately adjoining the districts mentioned in the
first reports (see ProMED-mail post no. 20030528.1307).

Maps
Bhutan:
<http://www.m-w.com/maps/images/maps/bhutan_map.gif> and
<http://healthmap.org/promed?v=27.4,90.4,5>
Bhutan districts:
<http://en.wikipedia.org/wiki/Bhutan>
Worldwide distribution of _Ca. L. asiaticus_ (September 2006):
<http://www.eppo.org/QUARANTINE/bacteria/Liberobacter_asiaticum/LIBEAS_map.htm>

Worldwide distribution of the Asian greening vector _D. citri_ (Sept. 2006):
<http://www.eppo.org/QUARANTINE/insects/Diaphorina_citri/DIAACI_map.htm>

Pictures
Citrus greening symptoms and vector photo galleries:
<http://www.aphis.usda.gov/plant_health/plant_pest_info/citrus_greening/gallery.shtml>
and
<http://www.eppo.org/QUARANTINE/bacteria/Liberobacter_africanum/LIBESP_images.htm>


Links
Citrus greening information:
<http://www.aphis.usda.gov/plant_health/plant_pest_info/citrus_greening/index.shtml>,

<http://www.daff.gov.au/aqis/quarantine/naqs/naqs-fact-sheets/citrus-greening>
and
<http://www.bioone.org/perlserv/?request=get-document&issn=0015-4040&volume=087&issue=03&page=330>

Diversity of _Ca. L. asiaticus_ strains:
<http://aem.asm.org/cgi/content/abstract/71/11/6473>
_Ca._ L. asiaticus taxonomy:
<http://beta.uniprot.org/taxonomy/34021>
Information on the Asian vector:
<http://www.daff.gov.au/aqis/quarantine/naqs/naqs-fact-sheets/pests_of_plants_asian_citrus_psyllid>

Taxonomy of the Asian vector:
<http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=200477>

_Ca. L. americanus_ description:
<http://ijs.sgmjournals.org/cgi/content/abstract/55/5/1857>
- Mod.DHA]

See Also

Citrus diseases - Philippines, India: replanting 20080130.0375
2007
----
Huanglongbing, citrus - USA: (TX), vector quarantine 20071212.4000
Huanglongbing, citrus - Viet Nam, USA: new biocontrol 20070912.3018
Huanglongbing & citrus tristeza virus, citrus - Philippines (NV) 20070709.2175
Huanglongbing, citrus - Pakistan, US (FL) 20070616.1961
2006
----
Huanglongbing citrus - USA (FL) 20060322.0894
2005
----
Huanglongbing, citrus - USA (FL) (03) 20051102.3203
Huanglongbing, citrus - USA (FL) (02) 20051017.3035
Huanglongbing, citrus - USA (FL) 20050910.2683
Huanglongbing, citrus - Malaysia (Kota Samarahan) 20050404.0976
Huanglongbing, citrus - Brazil (SP State) 20050325.0859
2004
----
Citrus huanglongbing - East Timor, Indonesia (Papua) 20040923.2625
Huanglongbing, citrus - Brazil: new strain? 20040723.2012
2003
----
Citrus huanglongbing - Papua New Guinea (Sandaun) 20030528.1307
Citrus huanglongbing - Bhutan 20030404.0823
2002
----
Liberobacter, citrus greening - Papua New Guinea 20021127.5909
....................dha/ejp/dk

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