.

Date: January 10, 2008
Source: VietNamNet Bridge, Viet Nam News report [edited]
<http://english.vietnamnet.vn/tech/2008/01/763441/>

Sixty specialists from the International Rice Research Institute (IRRI), Cambodia, Indonesia, the Philippines, South Korea, and Viet Nam met to discuss how best to manage pest infestation and viruses that have affected rice crops in Viet Nam. During the workshop, the deputy minister for Agriculture and Rural Development (MARD), Dr Bui Ba Bong, said brown planthoppers infested the winter-spring crop of 2005-2006 in the Mekong Delta, leaving plants stunted, twisted, and with no grains. During last year's [2007] summer-autumn crop, some 400 hectares (988 acres) of rice fields in the Mekong provinces of Long An and Dong Thap were affected. Bong said the disease lowered the Mekong Delta's rice production by some 700 000 tonnes in 2006.

In response to Viet Nam's request, in May 2006 the Australian Centre for International Agricultural Research [ACIAR] funded a project that would help farmers overcome this crippling problem in a sustainable manner. Bong urged international scientists to help Viet Nam to develop a research plan and strategy that would not rely on pesticides and would be sustainable. "We need to ensure that Viet Nam will continue to enjoy high rice productivity with no damage to the environment," he said.

Dr IL Choi, a virologist from IRRI, said the pests and diseases could spread very rapidly and the virus[es] had been found far north of Hanoi. Prof MM Escalada, a communications scientist from the Philippines, said: "Rapid communication through use of multimedia will be useful. Viet Nam has shown to have high capacity in doing this efficiently." The director general of the MARD's Plant Protection Department, Nguyen Quang Minh, said the department would intensify vigilance through improved monitoring, and increase awareness and training campaigns to assist farmers in the coming seasons to combat the diseases.

--
Communicated by:
ProMED-mail
<promed@promedmail.org>

[Epidemics of planthoppers and leafhoppers infesting rice crops and spreading virus diseases were reported from this area recently.
Specifically, the Asian brown planthopper (_Nilaparvata lugens_) was reported to have reached very high numbers. It is one of the worst pests of rice in the Australasian and Pacific Island region and is also the vector of _Rice grassy stunt virus_ (RGSV; genus _Tenuivirus_) and _Rice ragged stunt virus_ (RRSV; genus _Oryzavirus_). Symptoms of both of these were observed associated with the planthopper epidemic. A number of other rice viruses spread by the green rice leafhopper (_Nephotettix virescens_) including _Rice yellow stunt virus_, _Rice tungro bacilliform virus_ and _Rice tungro spherical virus_ are also present in southern Viet Nam. Other viruses such as _Rice stripe virus_, _Rice dwarf virus_ and _Rice hoja blanca virus_ are spread by different species of plant- or leafhoppers. In tropical regions, levels of virus infection and vector density may be very high. Crop losses of up to 100 percent due to some virus diseases (for example tungro) have been reported.

Several of the insect-transmitted rice viruses are transmitted by their vectors in a persistent (vector infectious for life) or semi-persistent manner and can therefore be spread over long distances by infectious insects transported on air currents or by people movements. Generally for these pathogens, disease management includes vector control, cultural practices to minimise inoculum, and the use of rice varieties resistant to the vector, the virus, or both. Cultivars resistant to the vectors have usually low virus disease incidence.

At least 15 viruses are known to affect rice, and many of these occur in Asia. Virus disease problems seem to have been accentuated worldwide by the introduction of modern agricultural techniques, double cropping and high yielding rice cultivars. The pathogens may have been present, but rarely reached epidemic proportions under traditional cropping systems when average rice yield was low.

Maps
Viet Nam:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/vietnam_pol01.jpg>  and
<http://healthmap.org/promed?v=14.9,108.5,5>
Viet Nam provinces:
<http://www.angelfire.com/co/hongnam/vnmap.html>
Distribution of several rice viruses in southern Viet Nam:
<http://www.kper.or.kr/img/board/75ho_info_05.jpg>

Pictures
Brown planthoppers:
<http://www.agric.nsw.gov.au/Hort/ascu/fulgor/nlugens.htm>  and
<http://www.dpvweb.net/dpv/showfig.php?dpvno=320&figno=03>
RGSV symptoms:
<http://seedcenter17.doae.go.th/farmer/pest/Image_Disease/rice_grassy%20stunt-05-014_B.jpg> 
and
<http://www.dpvweb.net/dpv/showfig.php?dpvno=320&figno=04>
RRSV symptoms:
<http://www.ricethailand.go.th/rkb/data_005/Image_Disease/rice_ragged%20stunt-05-012_B.jpg>
Rice tungro disease:
<http://www.last.gov.cn/OA/upload/other/200742010053532.bmp>

Links
Review of rice viruses, biology and epidemiology:
<http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.phyto.34.1.249?journalCode=phyto>
Illustrated fact sheets for all major diseases and pests of rice via:
<http://www.knowledgebank.irri.org/RiceDoctor/default.htm>
List of rice diseases and pathogens:
<http://www.apsnet.org/online/common/names/rice.asp>
Taxonomy and descriptions of rice viruses via:
<http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/index.htm>
_N. lugens_ taxonomy and distribution map:
<http://www.environment.gov.au/cgi-bin/abrs/fauna/details.pl?pstrVol=FULGOROIDEA;pstrTaxa=1909;pstrChecklistMode=2>
IRRI:
<http://www.irri.org>
ACIAR:
<http://www.aciar.gov.au/home>.  - Mod.DHA]

[see also in the archive:
2007
----
Rice grassy stunt virus - Viet Nam (Mekong Delta) 20070725.2382
Virus disease, rice - Viet Nam (02) 20070614.1939
Virus disease, rice - Viet Nam 20070611.1899
2006
----
Ragged and grassy stunt, brown planthopper, rice - Viet Nam 20061103.3157]
 

The news item on this page is copyright by the organization where it originated - Fair use notice

Other news from this source