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Published Date: 2018-02-08 20:17:05
Subject: PRO/PL> Asian greening, citrus - China
Archive Number: 20180208.5616524
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Mon 5 Feb 2018
Source: Fresh Plaza [edited]

Citrus greening disease caused a drop of 70-80 per cent for Gannan [Gansu Province] navel oranges. Since 2012, these areas have suffered from a widespread outbreak of citrus greening disease.

China's major [citrus] production area has already moved north. The main advantage is that the weather is relatively cold, which limits the spread of citrus greening disease. Farmers have gradually deepened their understanding of this disease. They are able to adopt effective management.

The overall production volume is relatively stable. Government departments continuously implement severe measures to restore production areas that have suffered greatly from citrus greening disease.

Communicated by:

Date: Tue 6 Feb 2018
Source: Xinhuanet [edited]

Across China, farmers fight against [a] global "citrus killer". Blood orange growers in Lianjiang [Fujian province] have long ditched chemical fertilizers to help their groves survive "the yellow dragon," a deadly disease threatening citrus groves. In China, the disease, also known as Huanglongbing, wreaks havoc in more than 10 citrus-growing regions.

In 1993, a yellow dragon outbreak nearly exterminated blood orange groves in Lianjiang, leaving only hundreds of hectares alive. Growers spent more than 10 years recovering their groves to a total of 5000 hectares, but another epidemic in 2007 destroyed them again.

The government started subsidizing bacteria-free saplings produced by a breeding center since 2010, because no one knew whether saplings then traded in the market, all grown by farmers themselves, were clean or not. Around 80 per cent of the cost of a bacteria-free sapling is covered by the government. A farmer only needs to pay half the price of a traditional sapling. The measures [also] include use of organic fertilizers, equipment that captures psyllids, early detection and handling of sick trees.

Communicated by:

[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. Control using cultural methods, such as interplanting with non-host crops, is 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).

China provinces:

Asian greening (HLB) symptoms, leaves and branches:, and
Asian greening, fruit symptoms:, and
Asian and African greening, symptoms and vector photo galleries: and
_D. citri_:

Citrus greening information:,, and
Asian greening, information and distribution:
African greening, information and distribution:
Taxonomy of Liberibacter species via:
Taxonomy and information for psyllid vectors (with pictures) via: and
- Mod.DHA]

See Also

Asian greening, citrus - Panama: 1st rep (BC) 20170707.5157200
Asian greening, citrus - Trinidad & Tobago: 1st rep 20170614.5104395
Asian greening, citrus - Mexico: (OA) 20170502.5007425
Asian greening, citrus - China: (southern) 20170120.4778384
Asian greening, citrus - Nepal: (KS) 20161129.4660906
Asian greening, citrus - Tanzania: susp 20160912.4481387
Huanglongbing, citrus - Colombia: (LG) 20160209.4005503
Huanglongbing, citrus - Portugal: (AL) susp. 20151116.3796582
Huanglongbing, citrus - India: survey 20150409.3285806
Huanglongbing vector, citrus - Europe: 1st rep, Spain (GA) 20150213.3163555
Huanglongbing, citrus - Paraguay 20130724.1842707
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
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