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 31 Jul 2009
Source: Viet Nam News (VNS), Nhan Dan (The People) report
[edited] <http://vietnamnews.vnagency.com.vn/showarticle.php?num=01DOM310709>
Brown planthoppers have destroyed 6700 hectares [approx. 16 600
acres] of summer-autumn rice in central provinces, leaving crops
with ragged and stunted-rice disease. The pest infestation has
also ruined several thousand hectares of rice fields in northern
and southern provinces.
Agricultural authorities have urged farmers to take preventive
measures, including spraying pesticides, spreading fertilizers,
and transplanting rice seedlings on schedule to prevent the
spread of the disease in rice fields.
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[_Rice ragged stunt virus_ (RRSV; genus _Oryzavirus_) is known
from a number of countries in Asia with reported yield losses of
up to 90 percent. 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 planthoppers (_Nilaparvata lugens_). The
insects transmit the virus in a persistent manner (RRSV
replicates in the vector and is retained during molting), but
the virus is not passed on to the progeny through eggs. Insects
carrying RRSV remain infectious for life and can be transported
on air currents to spread the virus quickly over long distances.
Besides rice (_Oryza sativa_), other species in the genus can
also be affected.
In tropical regions, especially where rice is grown all year
round, levels of rice virus infection and vector density may be
very high. Disease management for rice viruses includes cultural
practices, vector control, and use of cultivars with reduced
sensitivity or resistance to the virus, the vector, or both.
Cultivars resistant to the vector have low disease incidence.
The application of insecticides to migratory planthoppers is
being used in some areas to reduce disease incidence.
_N. lugens_ is one of the worst pests of rice in the
Australasian and Pacific Island region. In addition to being a
virus vector, it causes yellowing, browning, and drying of
plants ('hopper burn') and leaves small injuries exposing the
plant to fungal and bacterial infections. Besides RRSV, it is
also a vector of several other rice viruses. Additional rice
viruses are transmitted by other sap sucking leaf- and
planthoppers (_Nephotettix_ and _Laodelphax_ species). An
epidemic of _L. striatellus_, the vector of the very damaging
_Rice stripe virus_, has been reported recently from northern
Viet Nam (ProMED-mail post 20090608.2118).
Maps
Map of Viet Nam and neighbours:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/vietnam_pol01.jpg>
<http://healthmap.org/r/008c>
Viet Nam provinces:
<http://www.angelfire.com/co/hongnam/vnmap.html>
Pictures
RRSV symptoms:
<http://plantpro.doae.go.th/diseasegroup/rice/ragged/r_ragg25.jpg>
_N. lugens_:
<http://www.dpvweb.net/dpv/showfig.php?dpvno=320&figno=03>
Links
Ragged stunt disease information:
<http://www.knowledgebank.irri.org/ricedoctor/Fact_Sheets/Diseases/Rice_Ragged_Stunt.htm#top>
RRSV description and taxonomy:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.060.0.09.003.htm>
Brown planthopper information:
<http://www.knowledgebank.irri.org/RiceDoctor/Fact_Sheets/Pests/Planthopper.htm#Common>
Additional information on rice hoppers and viruses via:
<http://www.knowledgebank.irri.org/RiceDoctor/Welcome_to_Rice_Doctor.htm>
Research on hopper resistance:
<http://www.shigen.nig.ac.jp/rice/rgn/vol21/b23.html>
Review of rice viruses biology and epidemiology:
<http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.phyto.34.1.249?journalCode=phyto>.
- Mod.DHA][see also
in the
archive:
Rice viruses - Viet Nam: alert 20090608.2118
2008
----
Rice diseases - Viet Nam 20081017.3291
Virus diseases, rice - Viet Nam: update (02) 20080322.1093
Virus & blast diseases, rice - Viet Nam (Mekong Delta)
20080204.0454
Virus diseases, rice - Viet Nam: update 20080118.0221
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] |
|
