Sydney NSW, Australia
For your information
2018-07-18T18:00:00.0000000Z
   0
VIRUS AND BLAST DISEASES, RICE - VIET NAM: (MEKONG DELTA)

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: Thu 21 Jun 2018
Source: VietnamNet [edited]
<http://m.english.vietnamnet.vn/fms/society/202815/delta-summer-autumn-rice-planted-too-early--threatened-by-diseases.html>

Farmers in the Mekong Delta who sowed the summer - autumn rice crop
early are facing a threat of disease outbreaks. Nguyen Van Hien, Plant
Cultivation and Protection, said [that] unfavourable weather has
brought rice diseases which could hit yields. Diseases often occur
when rice is sowed early or late since brown-plant hoppers and other
pests from unharvested fields from the previous crop move to the newly
sowed fields, he said.

In Dong Thap Province some 560 ha sowed early have been affected by
brown plant hoppers. [A farmer] said local agricultural officials did
warn they had to have a gap of at least 3 weeks between crops to
eliminate diseases. "But since the price of rice was high, farmers
here sowed early."

In Kien Giang Province, more than 252 140 ha have been planted, with
15 500 ha being affected by diseases such as rice grassy stunt, rice
ragged stunt and rice blast. 

Plant Cultivation and Protection has instructed district bureaus to
regularly report about diseases and warned farmers to destroy rice
plants which are severely affected. This [2018] summer - autumn the
delta has planted more than 1.65 million ha, according to the Ministry
of Agriculture and Rural Development. 
--
Communicated by:
ProMED-mail
<promed@promedmail.org>

[Rice viruses
------------
_Rice ragged stunt virus_ (RRSV; genus _Oryzavirus_) has been reported
to cause yield losses of up to 90 per cent in several Asian countries.
Symptoms include ragged appearance of plants, twisted leaves, vein
swelling, unfilled grains and severe stunting of plants. Its only way
of spread is vector transmission by brown plant hoppers (BPH;
_Nilaparvata lugens_). The insects transmit the virus in a persistent
manner and remain infectious for life. Infected hoppers can be
transported on air currents to spread the virus quickly over long
distances.

_Rice grassy stunt virus_ (RGSV; genus _Tenuivirus_) has been reported
to cause serious damage in limited areas during sporadic outbreaks of
its vector. It is spreading in large parts of the rice-growing areas
of Asia. RGSV is also transmitted exclusively by vectors (_N. lugens_
and other species in the genus) in the same way as RRSV. Symptoms
include severe stunting, excessive tillering ('grassy' appearance),
erect growth habit, leaf spots and reduced pale leaves. Infected
plants usually survive until maturity, but produce no panicles.

A number of other rice viruses (several also present in the region)
are spread by different species of plant - or leaf hoppers. In
tropical regions, levels of virus infection and vector density may be
very high. High vector populations are often associated with virus
outbreaks with crop losses of up to 100 per cent reported. In its own
right, BPH causes yellowing, browning and drying of plants ('hopper
burn') and leaves small injuries exposing the plant to fungal (such as
rice blast) and bacterial infections.

Disease management for these viruses includes cultural practices (such
as short term draining of rice fields, crop rotation, or rice-free
periods), vector control and use of cultivars with reduced sensitivity
or resistance to the virus, the vector, or both. Crop cultivars
resistant to BPH have low disease incidence, but insect adaptation
overcoming plant resistance has been a problem. The application of
insecticides to migratory plant hoppers is being used in some areas to
reduce disease incidence.

Rice blast
----------
Rice blast is caused by the fungus _Pyricularia oryzae_ (previously
_Magnaporthe oryzae_). It is one of the most destructive diseases of
the crop worldwide, with potential yield losses of more than 50 per
cent. Symptoms include lesions on all parts of the shoot, as well as
stem rot and panicle blight. When nodes are infected, all plant parts
above the infection die and yield losses are severe. When infection
occurs at the seedling or tillering stages, plants are often
completely killed; infection late in the growth cycle generally leads
to less severe damage. Depending on which plant parts are affected,
the disease may manifest itself as leaf, collar, node, or neck blast.
More than 50 species of grasses and sedges can be affected by related
pathogens, but most strains isolated from rice can only infect a
limited number of cultivars.

The fungus also causes wheat blast (for example, see ProMED-mail posts
http://promedmail.org/post/20170306.4883233 and
http://promedmail.org/post/20170123.4784298). Although the pathogens
are currently classified as the same species, the wheat blast pathogen
is a distinct population (referred to as _P. oryzae_ Triticum
population) and does not cause disease in rice.

Symptom severity and spread of the blast fungus are influenced by
climatic conditions, including high humidity. The disease is also
favoured by high nitrogen levels (for example from fertilizers). The
fungus is spread by infected plant debris, mechanical means (including
insect activity), water and wind. Disease management may include
fungicides and cultural practices but relies mainly on resistant
varieties. However, the fungus is highly variable and this favours the
emergence of new strains with increased virulence. Use of certified
clean seed is essential, and farm saved seed poses a high risk of
carry-over of the fungus to subsequent crops.

Maps
Viet Nam and neighbours:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/vietnam_pol01.jpg>
Viet Nam provinces:
<http://en.wikipedia.org/wiki/File:VietnameseProvincesMap.png>

Pictures
RRSV symptoms:
<http://farmextensionmanager.com/English/Rice%20technology%20bank/pest%20doctor/images/ragged%20stunt%20virus.jpg>,
<http://eagri.org/eagri50/PATH272/lecture01/0024.jpg> and
<http://www.knowledgebank.irri.org/images/stories/ragged-stunt-1.jpg>
RGSV symptoms:
<http://www.knowledgebank.irri.org/images/stories/rice-grassy-stunt.jpg>,
<http://agritech.tnau.ac.in/crop_protection/images/rice_diseases/grassy%20stunt%20disease.jpg>
and
<http://www.dpvweb.net/dpv/showfig.php?dpvno=320&figno=04>
Rice blast symptoms:
<http://www.knowledgebank.irri.org/ricebreedingcourse/blast.jpg>
(different symptomatic forms) and
<http://www.imtech.res.in/raghava/rbpred/lesion.jpg>
Rice fields affected by blast:
<http://ucanr.edu/blogs/riceblog/blogfiles/22977_original.jpg> and
<https://previews.123rf.com/images/imagethink/imagethink1411/imagethink141100067/33260576-rice-blast-Stock-Photo.jpg>
Brown plant hoppers:
<http://www.dpvweb.net/dpv/showfig.php?dpvno=320&figno=03>

Links
Information on RRSV:
<http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/diseases/item/rice-ragged-stunt>,
<https://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=47647>,
<https://www.genome.jp/virushostdb/42475> and
<http://sdb.im.ac.cn/vide/descr691.htm>
Information on RGSV:
<http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/diseases/item/rice-grassy-stunt>,
<https://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=47614>,
<http://agritech.tnau.ac.in/expert_system/paddy/cpdisstunragg.html>
and
<https://www.sciencedirect.com/science/article/pii/S0168170214001701>
Virus taxonomy via:
<https://talk.ictvonline.org/taxonomy/>
Brown plant hopper information via:
<http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/insects/item/planthopper>
(with pictures)
Information on rice blast:
<http://www.knowledgebank.irri.org/training/fact-sheets/pest-management/diseases/item/blast-leaf-collar>
(with pictures),
<http://www.oisat.org/pests/diseases/fungal/rice_blast.html>,
<http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=46103>
and
<http://www.imtech.res.in/raghava/rbpred/home.html>
Rice blast disease cycle:
<http://www.imtech.res.in/raghava/rbpred/cycle.jpg>
Impact of rice blast (and other fungal crop diseases):
<http://onlinelibrary.wiley.com/doi/10.1111/j.1364-3703.2011.00783.x/full>
_P. oryzae_ taxonomy and synonyms:
<http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=224486>
and
<http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=224486>.
- Mod.DHA

HealthMap/ProMED map available at:
Mekong Delta, Vietnam: <http://healthmap.org/promed/p/3719>]

[See Also:
Blast disease, rice - Bangladesh: (RJ)
http://promedmail.org/post/20180419.5756531
2017
----
False smut & blast, rice - Bhutan, India
http://promedmail.org/post/20171102.5419405
Black streaked dwarf disease, rice - Viet Nam: (TB, NA)
http://promedmail.org/post/20171005.5363723
Blast disease, rice - India: (JK)
http://promedmail.org/post/20170725.5202371
2016
----
Blast disease, wheat & rice - Bangladesh
http://promedmail.org/post/20160419.4168271
Blast disease, rice - India (02): (JK) origin
http://promedmail.org/post/20160407.4145967
Blast disease, rice - India: (TN)
http://promedmail.org/post/20160108.3918812
2015
----
Rice diseases - Malaysia: (western) emerging strains
http://promedmail.org/post/20150108.3080315
2014
----
Blast disease & bacterial blight, rice - Viet Nam: Mekong Delta, alert
http://promedmail.org/post/20140216.2282042
2011 
----
Black streaked dwarf, rice - Viet Nam: (TT, QT)
http://promedmail.org/post/20110322.0897
2010 
----
Rice yellow stunt virus - Viet Nam: (BG)
http://promedmail.org/post/20101018.3772
Multiple disease, rice - Viet Nam (03)
http://promedmail.org/post/20100816.2835
Ragged & grassy stunt viruses, rice - Thailand
http://promedmail.org/post/20100628.2155
Black streaked dwarf, rice - Viet Nam (02): spread
http://promedmail.org/post/20100506.1473
Ragged & grassy stunt viruses, rice - Indonesia: (JB)
http://promedmail.org/post/20100409.1145
Black streaked dwarf, rice - Viet Nam: alert
http://promedmail.org/post/20100406.1099
Multiple disease, rice - Viet Nam (02)
http://promedmail.org/post/20100322.0906
Multiple disease, rice - Viet Nam
http://promedmail.org/post/20100307.0749
Undiagnosed diseases, rice - Viet Nam: (northern)
http://promedmail.org/post/20100114.0162
2009 
----
Ragged stunt, rice - Viet Nam
http://promedmail.org/post/20090803.2722
Rice viruses - Viet Nam: alert
http://promedmail.org/post/20090608.2118
and additional items in the archives]
.................................................sb/dha/ec/ml
*##########################################################*
************************************************************
ProMED-mail makes every effort to  verify  the reports  that
are  posted,  but  the  accuracy  and  completeness  of  the
information,   and  of  any  statements  or  opinions  based
thereon, are not guaranteed. The reader assumes all risks in
using information posted or archived by  ProMED-mail.   ISID
and  its  associated  service  providers  shall not be  held
responsible for errors or omissions or  held liable for  any
damages incurred as a result of use or reliance upon  posted
or archived material.
************************************************************
Donate to ProMED-mail. Details available at:
<http://www.isid.org/donate/>
************************************************************
Visit ProMED-mail's web site at <http://www.promedmail.org>.
Send all items for posting to: promed@promedmail.org (NOT to
an individual moderator).  If you do not give your full name
name and affiliation,  it may not be posted.  You may unsub-
scribe at  <http://ww4.isid.org/promedmail/subscribe.php>.
For  assistance  from   a   human   being, send mail to:
<postmaster@promedmail.org>.

ProMED
Rice
Viruses
Blast
Vietnam

No responses yet...