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Published Date: 2017-05-02 06:09:47
Subject: PRO/PL> Asian greening, citrus - Mexico: (OA)
Archive Number: 20170502.5007425

ASIAN GREENING, CITRUS - MEXICO: (OAXACA)
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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: Fri 28 Apr 2017
Source: FreshPlaza [edited]
http://www.freshplaza.com/article/174637/Mexico-HLB-pest-decreases-Oaxacas-lime-production-by-40-procent


[Asian greening disease] reduced Oaxaca's lime production by 50 000 tons, which accounts for 40 per cent of the state's total. The pest is currently present in 2000 hectares [about 4942 acres] of citrus, that is, 20 per cent of the plantations. As a result, lime prices have increased, stated Joaquin Fernandez Grajales, citrus product system civil association.

He said that Oaxaca was the country's 3rd biggest producer of Mexican and Persian limes. The disease was only detected in Mexico in July 2009 [in Yucatan; see ProMED-mail post 20090720.2570]. "Since there is no chemical or natural insecticide to combat this pest, the orchards are monitored and producers are given recommendations to manage it."

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communicated by:
ProMED-mail
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[Greening is one of the most damaging diseases of citrus crops affecting leaves and fruit. It is caused by fastidious phloem-inhabiting bacteria classified as _Candidatus_ Liberibacter asiaticus (Asian greening; huanglongbing, HLB), africanus (including a subsp. capensis; African greening) or americanus (South American greening). The 3 pathogens can only be distinguished by molecular methods.

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.

The diseases are restricted to _Citrus_ and close relatives because of the narrow host range of their psyllid vectors. _Ca._ L. asiaticus and americanus are spread by the Asian citrus psyllid (_Diaphorina citri_). The main vector for _Ca._ L. africanus is the African citrus psyllid _Trioza erytreae_. The pathogens can also be spread by grafting and possibly by seed from infected plants or transovarially in the vectors. Both pathogens and vectors can be spread with plant material.

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. Alternative management approaches, such as detection of infected trees by sniffer dogs and cultural control by interplanting with non-host crops, are being trialled. In areas where a pathogen has not yet been detected, biological control of vectors has been used successfully to reduce insect numbers and, therefore, the risk of greening outbreaks (for example, see ProMED-mail post 20090601.2034).

Maps
Mexico (with states):
http://www.lib.utexas.edu/maps/americas/mexico_pol97.jpg and
http://healthmap.org/promed/p/51981
North America, overview:
http://geology.com/world/north-america-map.gif

Pictures
Asian greening (HLB) symptoms:
http://www.caes.gov.tw/english/images/plant_02_5.jpg
Asian & African greening, symptoms and vector photo galleries:
https://gd.eppo.int/taxon/LIBEAF/photos and
http://www.invasive.org/browse/subinfo.cfm?sub=4695
_Ca._ L. asiaticus in host phloem, microscopy:
http://www.apsnet.org/publications/apsnetfeatures/Article%20Images/Huanglongbing_Fig21.jpg
_D. citri_:
https://entomologytoday.files.wordpress.com/2016/02/diaphorina-citri-5006083-smpt-2.jpg?w=410

Links
HLB updates from other areas:
http://www.freshplaza.com/article/173427/Huanglongbing-not-in-South-Africa-but-present-in-Africa and
https://californiaagtoday.com/huanglongbing-concern/
Citrus greening information:
http://cisr.ucr.edu/citrus_greening.html,
http://www.bioone.org/perlserv/?request=get-document&issn=0015-4040&volume=087&issue=03&page=330, and
http://ecoport.org/ep?SearchType=slideshowViewSlide&slideshowId=197
Asian greening, information and distribution:
http://www.cabi.org/isc/datasheet/16565
African greening, information and distribution:
http://www.cabi.org/isc/datasheet/16564
Taxonomy of Liberibacter species via:
http://www.uniprot.org/taxonomy/34019
Taxonomy and information for psyllid vectors (with pictures) via:
http://www.psyllids.org/index.htm and
http://www.psyllids.org/psyllidsMorphology.htm
- Mod.DHA]



See Also

Asian greening, citrus - China: (southern) 20170120.4778384
2016
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Asian greening, citrus - Nepal: (KS) 20161129.4660906
Asian greening, citrus - Tanzania: susp 20160912.4481387
Huanglongbing, citrus - Colombia: (LG) 20160209.4005503
2015
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Huanglongbing, citrus - Portugal: (AL) susp. 20151116.3796582
Huanglongbing, citrus - India: survey 20150409.3285806
Huanglongbing vector, citrus - Europe: 1st rep, Spain (GA) 20150213.3163555
2013
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Huanglongbing, citrus - Paraguay 20130724.1842707
2012
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Huanglongbing, citrus - Brazil: (SP) update 20121114.1408468
Huanglongbing, citrus - Argentina: 1st rep, (MN) 20120917.1296650
Huanglongbing, citrus - USA: (CA) 20120404.1089672
Huanglongbing, citrus - USA: (TX) spread 20120122.1017941
2011
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Huanglongbing, citrus - Costa Rica: 1st rep 20110223.0593
and older items in the archives
.................................................sb/dha/mj/sh
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