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: 1 September 2008
Source: Sun Star [edited]
<http://www.sunstar.com.ph/static/gen/2008/09/01/news/tungro.virus.hits.south.cotabato.html>

Tungro virus hits South Cotabato

Agriculture experts in South Cotabato province have warned farmers in the area to refrain from planting 2 varieties of palay [unhusked rice] at this time because of the onslaught of the tungro virus. Reynaldo H Legaste, provincial agriculture chief, said palay varieties RC 64 and RC 118 have been ravaged by tungro. "Not all varieties are performing at this time, so please refrain from planting those 2 varieties. Almost the whole of South Cotabato has been affected by tungro. Many palay fields have turned yellow-orange," he said.

Tungro, Legaste noted, is worse than the black bugs that infested the province's nearly 2500 hectares (about 6200 acres) of palay fields worth around PHP 4.5 million [USD 96 393] in the few months leading to April 2008. The provincial agriculture office has yet to release the damage wrought by the tungro disease, which is primarily spread by 2 species of green leafhoppers (_Nephotettix malayanus_ and _Nephotettix virescens_).
Worst hit by tungro is the farming town of Norala in the 2nd district of South Cotabato, the official reported.

Legaste blamed the resurgence of tungro in the province on the continuous palay planting in the area, which was prompted by the high prices of rice back then. "Farmers should have given the lands a rest even for one cropping season," he added. To help farmers from being hit by the tungro virus, Legaste dangled government-subsidized certified seeds. The province has a certified rice seed inventory of 2600 bags that can be available to farmers at half the commercial price, he added.

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

[Tungro is one of the most damaging rice diseases in South East Asia with reported losses of up to 100 per cent, and it is spreading in the region.
It is a syndrome (co-infection) involving _Rice tungro bacilliform virus_ (RTBV; genus _Tungrovirus_, family _Caulimoviridae_) and _Rice tungro spherical virus_ (RTSV; genus _Waikavirus_, family _Sequiviridae_).
Symptoms include leaf discolouration, stunting, reduced tillering, and few or no grains are produced. Only _Oryza_ species are natural hosts, but some other grasses are susceptible to vector inoculation under experimental conditions.

Tungro disease is transmitted by leafhoppers, the most efficient vector being the green leafhopper _Nephotettix virescens_. RTBV cannot be transmitted unless RTSV is present. After acquiring the viruses the vectors can immediately transmit the disease to other plants. All growth stages of rice are susceptible. Infectious vector insects transported on air currents or by people movements can spread the viruses over long distances. Disease management includes vector control, crop rotation, and other cultural practices to minimise inoculum, and the use of rice varieties resistant to the vectors, the virus, or both. Vector adaptation on leafhopper resistant varieties has been a problem, but virus resistant varieties from the Philippines and other countries are available.

The use of certified seed, as suggested above, is certainly advisable to prevent spread of other pathogens, but seed certification will not prevent tungro because the disease is not seed transmitted. At present the use of virus resistant varieties is considered the most economical means of managing the disease.

Maps
Philippines:
<http://www.ac.wwu.edu/~fasawwu/resources/img/map-philippines.png> and <http://healthmap.org/promed?v=11.7,122.9,5>
Philippine provinces:
<http://www.reliefweb.int/mapc/asi_se/cnt/phil/phl_ad.html>
Location of Norala:
<http://www.tageo.com/index-e-rp-v-70-d-m3365090.htm?Norala>
Pictures
Tungro symptoms on rice plant:
<http://www.last.gov.cn/OA/upload/other/200742010053532.bmp>  and <http://www.irri.org/media/achievements/images/Tungro.jpg>
Tungro-affected rice field:
<http://www.knowledgebank.irri.org/RiceDoctor/image26.jpg>
Green rice leafhopper:
<http://www.knowledgebank.irri.org/RiceDoctor/image74.jpg>  and
<http://www.sut.ac.th/e-texts/Agri/insectfinal2/Insects%20web/Images/chapter2_6_clip_image002.jpg> 

Links
Information on tungro disease:
<http://www.knowledgebank.irri.org/RiceDoctor/Fact_Sheets/Diseases/Tungro.htm>
<http://www.ias.ac.in/currsci/oct252003/1143.pdf>
_Rice tungro spherical virus_ taxonomy:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.065.0.02.004.htm>
_Rice tungro bacilliform virus_ taxonomy:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.015.0.04.001.htm>
Green leafhopper information:
<http://www.knowledgebank.irri.org/RiceDoctor/Fact_Sheets/Pests/Green_Leafhopper.htm> 

_N. virescens_ taxonomy:
<http://www.ento.csiro.au/aicn/system/c_1482.htm>
International Rice Research Institute (IRRI):
<http://www.irri.org> . - Mod.DHA]