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Date: Thu 23 Apr 2009
Source: The Gleaner (Kentucky) [edited]
<http://www.courierpress.com/news/2009/apr/23/soybean-rust-fungus-survived-winter/?partner=RSS>

The US soybean rust distribution map looks significantly different from a year ago [2008], said a plant pathologist in the University of Kentucky College of Agriculture. For the 1st time, soybean rust has overwintered on kudzu without any break in detection in Alabama, Georgia, and Louisiana.

This is an important development for 2 key reasons. First, infected kudzu could serve as a springboard for movement of soybean rust to soybeans under the right weather conditions.

Also, it is very common for storm systems to originate in the central Gulf area. These storms commonly blow up the Mississippi River Valley and into Kentucky. When there is significant disease activity in the central Deep South, spores of the rust fungus commonly move in high numbers across a broad span of northern production areas.

If this occurs early enough in the growing season, serious crop damage could ensue. Only time will tell what, if any, effects the overwintering has on soybean rust distribution or the 2009 soybean crop.

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[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. Fungicides may be used in disease management, and partially resistant soybean lines are available. However, new fungal strains with increased virulence and fungicide resistances are emerging.

The disease was introduced into the USA in 2004 where it overwinters in southern regions. Spores are carried northwards by prevailing winds every season, and by the end of 2007 they had been reported as far north as Canada. The new pathogen reservoir reported above provides now a more northerly base for spore release. This may increase the risk of spread earlier in the season, which would incur more serious damage than later crop infections.

A related, but less virulent species (_P. meibomiae_) is found in South America and the Caribbean causing similar symptoms.

Maps
USA:
<http://www.mapsofworld.com/usa/usa-road-map-enlarge-view.html>  and <http://healthmap.org/r/008w>
US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>

Pictures
Leaf rust on soybean:
<http://www.ent.iastate.edu/images/plantpath/soybean/asianrust/asian_soyrust_lesions.jpg>
and
<http://www.state.nj.us/agriculture/plant/soybeanrust.jpg>
Electron microscopy of leaf rust spores:
<http://www.wbhm.org/pics/features/soybean-spores.jpg>

Links
Additional news story:
<http://southeastfarmpress.com/soybeans/soybean-rust-0424/>
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/>
_P. pachyrhizi_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=121037>
Rust background, tracking, and current US distribution:
<http://www.usda.gov/soybeanrust/>,
<http://www.stopsoybeanrust.com/>, and
<http://www.sbrusa.net/>  - Mod.DHA]

[see also in the archive:
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 - Mexico: 1st report 20060219.0546
2005
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Soybean rust, Asian strain - Americas: alert 20050528.1476
2004
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Soybean rust - USA: 1st report 20041110.304 and older items in the archives]