A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
In this posting:
[1] Illinois
[2] Indiana
[3] Iowa
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[1] Illinois
Date: Mon 5 Oct 2009
Source: The Times (Illinois) [summ. & edited] <http://mywebtimes.com/archives/ottawa/display.php?id=388713>
Soybean fields having problems with white mold disease
Soybean producers in northern Illinois have experienced problems with a disease called sclerotinia stem rot, or white mold, this year [2009]. The disease is most severe in years that have wet, cool conditions during the flowering period, especially in fields or portions of fields that have restricted air movement, such as drilled or other field situations where the canopy has closed quickly.
The disease is characterized by dead plants that appear in midseason and have a white fungal mold growing on dead tissue of the stem, often just above the soil line. No soybean varieties are completely resistant to white mold, but some are less susceptible than others.
Currently, 2 foliar fungicides are registered [in the USA] for control of white mold in soybeans. A biological control product containing a parasite of the white mold fungus's sclerotia is also being studied at the University of Illinois.
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[2] Indiana
Date: Fri 2 Oct 2009
Source: Indiana Prairie Farmer [summ. & edited] <http://indianaprairiefarmer.com/story.aspx?s=31997&c=9>
White mold stings northern Indiana soybean fields
The disease can produce heavy yield losses. It was once a rare disease in Indiana soybeans but isn't so rare any more. It seems to be prevalent this year [2009], especially in northern and northwest Indiana. It's a disease that also attracts attention in other states, especially in cooler climates [for Ohio see ProMED-mail post 20090817.2912].
The organism can persist in the soil once it invades an area. Then every time the field is in soybeans in rotation, there is the threat of infection. Weather conditions play a role in whether or not the disease becomes severe in any one year, and in the timing of the outbreak of the disease. One way farmers in northwestern Indiana have combated white mold is to revert to wider row spacing that provides for more air circulation within the soybean canopy.
[Byline: Tom Bechman]
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[3] Iowa
Date: Tue 29 Sep 2009
Source: Wallaces Farmer [summ. & edited] <http://wallacesfarmer.com/story.aspx?s=31912&c=9>
White mold, a disease that can drastically cut yields, started to get the attention of farmers in Iowa in late August [2009]. This year white mold disease is so widespread that agronomists report observing it in many soybean fields in southern Iowa, too.
In northern Iowa, patches of soybeans killed by this disease were so abundant that they were found in nearly every soybean field during a field day on [18 Sep 2009]. For most of the fields, the disease was scattered in small patches.
Harvest the diseased patches last to combat white mold.
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[White mould, or sclerotinia stem rot, of soybean is caused by _Sclerotinia sclerotiorum_. This fungus is one of the most nonspecific and successful of plant pathogens with around 400 known hosts. Symptoms vary on different hosts. On soybean, white fungal growth appears on the stems leading to wilting and final death of the plant. Severe yield losses have been reported in soybean and other affected crops.
The pathogen is primarily soil-borne and can survive for many years in soil as sclerotia. It is also spread by infected plant material (including seeds), mechanical means, and wind-borne spores. Risk of crop infection depends on the previous disease history of an area as well as weather conditions. Disease management includes mainly cultural practices (for example the wide row spacing mentioned above) and fungicide applications.
White mould has progressed in recent years to become a threat to soybean production in the US. This year (2009), it has also caused problems for peanut producers in the country in the state of Georgia (see link below).
Maps of USA:
<http://www.mapsofworld.com/usa/usa-state-and-capital-map.html>,
<http://www.mapsofworld.com/usa/usa-road-map-enlarge-view.html>, and <http://healthmap.org/r/00UV>
Pictures
White mould symptoms on soybean:
<http://www.ent.iastate.edu/images/plantpath/soybean/whitemold/
white_mold_stem.jpg>
and
<http://www.ent.iastate.edu/images/plantpath/soybean/whitemold/
3185.4whitemoldkill.jpg>
Stained microscopy of _S. sclerotiorum_ sexual spores:
<http://ag.arizona.edu/PLP/plpext/diseases/vegetables/lettuce/
lettsclero1.htm>
Links
Information on white mould on soybean:
<http://web1.msue.msu.edu/imp/mods1/fact9803.html> and <http://www.planthealth.info/whitemold_basics.htm>
White mould on peanut, USA (Georgia), news story September 2009:
<http://www.walb.com/Global/story.asp?S=11185752>
Information on _S. sclerotiorum_ and crop diseases:
<http://www.extento.hawaii.edu/kbase/Crop/Type/s_scler.htm>,
<http://anrcatalog.ucdavis.edu/pdf/8042.pdf>, and <http://www.cals.ncsu.edu/course/pp728/Sclerotinia/S_sclerotiorum.html>
_S. sclerotiorum_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=212553>.
- Mod.DHA]
[see also:
Fungal diseases, soybean - USA 20090817.2912
2008
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Vegetable diseases - UK 20081225.4066
Sclerotinia, sunflower - Canada: (MB) 20081106.3490 Sclerotinia, multicrop - UK 20081008.3187 Fungal diseases, wheat, oilseed rape - UK 20080930.3083 Verticillium wilt & sclerotinia, oilseed rape - UK 20080718.2180 Wheat stripe rust, oilseed rape sclerotinia - China 20080408.1297 Fungal diseases, potato - Bangladesh 20080107.0091
2004
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Sclerotinia blight, peanut - USA (TX) 20041001.2702
2002
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Sclerotinia spp., sunflower wilt - Spain 20020706.4677
2001
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Sclerotinia shoot blight, grapevine - Chile 20011103.2724
1999
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Crop diseases - Canada (Manitoba) 19990816.1417]
