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New strains of leaf rust on soybeans inBrazil

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A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases

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: Tue 28 Apr 2009
Source: AgWeb [edited]
<http://www.agweb.com/Blogs/BlogPost.aspx?src=SouthernView&PID=a4934cc5-1f5f-4cb1-9dd7-a5bc272ace41>

Asian rust spots increase in Brazil

Mato Grosso [MT] state is reaching 100 percent of soybeans harvested, and registers 9 percent more rust foci than for the last crop. In the whole of Brazil, so far there were 2810 sites with Asian rust registered. This is 34 percent more than last year.

In MT the number of samples submitted to laboratories increased by 70 percent, and in the whole country the monitoring program was also intensified on the same scale.

But the Ag Eng. Carlos Bortolini Jr warns the rust is getting more resistant each year, and so producers need to expend more investments in fungicide. In his point of view, Asian rust must be handled as an epidemic to be defeated.

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

[Leaf rust (also called soybean rust, Asian rust) caused by the fungus _Phakopsora pachyrhizi_ 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, but data are lacking on its establishment in Europe. Besides soybean, over 30 other species in the family of _Fabaceae_, including kudzu (_Pueraria lobata_), can also be affected and may serve as pathogen reservoirs.

Spores are spread locally by splashing rain, or by wind over long distances. Several epidemic cycles may occur in one cropping season. Fungicides may be used in disease management, but timing of applications is considered important. Partially resistant soybean lines are available. However, new fungal strains with increased virulence and fungicide resistances are emerging, as is being reported above from Brazil.

While the related species _P. meibomiae_ is also found in South America and the Caribbean causing similar symptoms, this species is less virulent and is not referred to as 'Asian' rust. The item above refers to _P. pachyrhizi_ which has been established in Brazil since 2002.

Maps of Brazil
<http://en.18dao.net/images/9/96/Map-Brazil.jpg> and <http://healthmap.org/r/008S>

Pictures
Leaf rust 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>
Electron microscopy of leaf rust spores:
<http://www.wbhm.org/pics/features/soybean-spores.jpg>

Links
Information on soybean rust:
<http://www.eppo.org/QUARANTINE/Alert_List/fungi/PHAKPA.htm>,
<http://ohioline.osu.edu/ac-fact/0048.html>, and
<http://nt.ars-grin.gov/taxadescriptions/factsheets/index.cfm?thisapp=Phakopsorapachyrhizi>
Disease history and background (with pictures):
<http://www.apsnet.org/online/feature/rust/>
History and evolution in Brazil:
<http://www.scielo.br/scielo.php?pid=S1415-47572008000500020&script=sci_arttext
and
<http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=157028>
_P. pachyrhizi_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=121037>. - Mod.DHA]

[see also in the archive:
Leaf rust, soybean - USA: update 20090428.1594
Leaf rust, soybean - Australia: (NSW) alert 20090407.1351
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
2006
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Soybean rust, Asian strain - Brazil 20060611.1628
Soybean rust - Mexico: 1st report 20060219.0546
2005
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Soybean rust, Asian strain - Uruguay 20050819.2435
Soybean rust - Argentina (Santa Fe)(02) 20050816.2397
Soybean rust, Asian strain - Argentina (Santa Fe) 20050617.1715
Soybean rust, Asian strain - Americas: alert 20050528.1476
Soybean rust, Asian strain - Argentina 20050119.0185
2004
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Soybean rust, Asian strain - Brazil 20041222.3374
Soybean rust, Asian strain - Brazil (multistate) 20041209.3266
Soybean rust, Asian strain - Brazil (PR) 20041129.3186
Soybean rust - USA: 1st report 20041110.304
Soybean rust - Colombia (Cali) 20040827.2393
2003
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Phakopsora pachyrhizi, soybean - Brazil 20031119.2873
Soybean rust - Brazil 20030426.1022
Soybean rust - Brazil (Mato Grosso & Bahia) 20030415.0917
Soybean rust - Brazil (Sao Paulo State) 20030124.0214
and older items in the archives]

 

 

 

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