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FROGEYE LEAF SPOT AND ASIAN LEAF RUST, SOYBEAN - ARGENTINA, BRAZIL
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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 Feb 2010
Source: Bloomberg Business Week [summ. Mod.DHA, edited]
<http://www.businessweek.com/news/2010-02-01/record-brazil-argentine-soy-crop-hurt-by-disease-week-ahead.html>
Record Brazil, Argentine soy crop hurt by disease
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Soybean fungi are spreading across Brazil and Argentina, the world's
2nd- and 3rd-largest producers, threatening record crops as demand
gains.
Argentine farmers confront an "unprecedented" outbreak of Frogeye Leaf
Spot, which can cut yields by 12 percent and has reached the heart of
the Pampas farmlands, said agronomist Luciano Ascheri, Argentine
Association of Regional Agricultural Experimentation Consortium.
Frogeye is relatively new to Argentina's soybean farms and thrives in
humid weather, he said. Downpours brought by the El Nino weather
system which broke a 2-year drought across Argentina, are driving up
the incidence of the fungus. Cases of frogeye, which last year [2009]
was confined to southern Cordoba, are now being found in Argentina's
main agricultural areas, Ascheri said.
In Brazil, more than 1200 cases of Asian Rust have been reported,
compared with 636 at this time last year, according to Claudia Godoy
of Embrapa, a government agricultural agency. Downpours caused by El
Nino encouraged the outbreak which may reduce supplies as global
consumption rises. In 2003-2004, the country's worst-ever outbreak
destroyed 8 percent of the crop.
Together, the 2 South American countries will export 33.9 million tons
of soybeans in 2010, compared with 37.4 million from the US. Both
Ascheri and Godoy declined to give estimates of how many tons of
soybeans may be lost because of the fungi.
[Byline: L Kassai and R Orihuela]
--
Communicated by:
ProMED-mail
<promed@promedmail.org>
[Frogeye leaf spot is caused by the fungus _Cercospora sojina_, which
can infect leaves, stems, and seeds of soybean. The pathogen is found
worldwide but is only problematic under warm, humid conditions.
Significant yield losses of 10 to 50 percent are commonly associated
with frogeye epidemics. The fungus is spread via infected plant
material and can also be seed borne leading to inferior seed quality.
Disease management includes use of disease-free seed, planting of
resistant varieties, crop rotation, tillage, and fungicide
applications. Frogeye is spreading in Argentina and is considered an
emerging threat to national soybean producers (ProMED-mail post
20090316.1070).
Asian leaf rust (also called soybean rust, Asian rust) of soybean is
caused by the fungus _Phakopsora pachyrhizi_ and can result in yield
losses of soybean crops of up to 70 percent. It is widespread in Asia
and Africa and spreading in the Americas. Over 30 other species of
_Fabaceae_ may serve as pathogen reservoirs. Spores are spread by
splashing rain or by wind over long distances. Fungicides may be used
in disease management, but timing of applications is considered
important. Partially resistant soybean lines are available. New fungal
strains with increased virulence and fungicide resistances are
emerging in Brazil (ProMED-mail post 20090501.1644) and other soybean
producing countries.
Maps
Argentina:
<http://media.maps.com/magellan/Images/ARGENT-W1.gif> and
<http://healthmap.org/r/007a>
Brazil
<http://en.18dao.net/images/9/96/Map-Brazil.jpg> and
<http://healthmap.org/r/008S>
South America, overview:
<http://www.worldatlas.com/webimage/countrys/sa.htm>
Pictures
Frogeye symptoms, upper leaf surface:
<http://www.ces.ncsu.edu/depts/pp/notes/Soybean/soy003/frogeye2.jpg>
Frogeye symptoms, leaf underside:
<http://extension.missouri.edu/explore/images/g04442frogeyebottom.jpg>
Leaf rust symptoms on soybean:
<http://www.ent.iastate.edu/images/plantpath/soybean/asianrust/asian_soyrust_lesions.jpg>,
<http://www.state.nj.us/agriculture/plant/soybeanrust.jpg>, and
<http://www.wbhm.org/pics/features/soybean-icon.jpg>
Links
Frogeye information:
<http://extension.agron.iastate.edu/soybean/diseases_frogeye.html> and
<http://www.ces.ncsu.edu/depts/pp/notes/Soybean/soy003/soy003.htm>
_C. sojina_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=119516>
Information on soybean leaf rust:
<http://ohioline.osu.edu/ac-fact/0048.html>,
<http://nt.ars-grin.gov/taxadescriptions/factsheets/index.cfm?thisapp=Phakopsorapachyrhizi>
and
<http://www.apsnet.org/online/feature/rust/>,
_P. pachyrhizi_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=121037>
- Mod.DHA]
[see also:
Asian leaf rust, soybean - Cuba: 1st rep. 20100204.0374
2009
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Fungal diseases, field crops - Americas 20091025.3696
Fungal diseases, soybean - USA 20090817.2912
Leaf rust, soybean - Brazil: new strains 20090501.1644
Leaf rust, soybean - USA: update 20090428.1594
Leaf rust, soybean - Australia: (NSW) alert 20090407.1351
Frogeye leaf spot, soybean - Argentina 20090316.1070
2008
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Soybean diseases - USA: (LA) 20081012.3231
Asian soybean rust - USA, Mexico: update 20080928.3070
2007
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Asian soybean rust - USA: 2007 final report 20071230.4184
Asian soybean rust - Canada: 1st report, (ON) 20071120.3751
Asian soybean rust - Congo DR: 1st report 20070917.3086
Asian soybean rust - Ghana: 1st report 20070820.2710
Frogeye leaf spot, soybean - USA: surveillance 20070627.2067
2006
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Soybean rust, Asian strain - Brazil 20060611.1628
Soybean rust - Mexico: 1st report 20060219.0546
and older items in the archives]
.......................................dha/ejp/jw
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