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	va1-sg19016.securesites.net

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SUDDEN DEATH SYNDROME, SOYBEAN - USA (NEBRASKA)

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Sudden death syndrome (SDS) has been found in many Nebraska soybean 

fields over the last two weeks. This disease was only first confirmed 

in the state in 2004. Calls and samples across the eastern half of 

Nebraska suggest the disease is widespread, but in most fields large 

areas are not affected.



Sudden death syndrome of soybean is caused by the fungus _Fusarium 

solani_ f. sp. _glycines_. This is a different fungus than the one 

that caused early season damping off problems associated with soybean 

stands. This year's weather with moisture in the early season and at 

the early reproductive stage has been conducive to SDS. It should be 

possible to see full symptom expression now.



Early planting favors SDS. With all the information on increasing 

yields with earlier planting, we expect to see more of this disease. 

Soil compaction and high fertility levels also have been associated 

with increased levels of SDS.



The foliar symptoms start with interveinal necrosis and the spots 

coalesce to form brown streaks between the leaf veins with yellow 

margins. Leaves eventually drop with the petiole (leaf stem) 

remaining attached. The root system will have a deteriorated tap-root 

and lateral roots will only be evident in the upper soil profile. The 

root cortex is light-gray to brown and may extend up the stem. 

Typically, plants can be pulled from the ground easily and will have 

a dark blue fungal growth on the roots. The blue color will not be 

evident in dry soil conditions.



At this time SDS appears to be widespread in Nebraska, but it can be 

effectively managed. If a large area of the field is affected, early 

planting should be avoided and resistant varieties used next year. 

Thus far, seed treatment has not been shown to be effective.





--

J. Allan Dodds





[SDS was 1st discovered in the USA (Arkansas) in 1972 and has now 

become widespread in soybean-growing regions in the United States, 

Argentina, and Brazil. Plants turn yellow and die quickly after pod 

set and symptoms often appear in patches in a field. Yield losses may 

be more than 80 percent, depending on variety and timing of 

infection. Appearance of SDS at early pod fill is reportedly more 

damaging than its appearance at a later stage of plant development. 

Yield reduction is the result of reduced photosynthetic area, 

defoliation, flower and pod abortion, and reduced seed size.



_Fusarium virguliforme_ (previously _F. solani_ f. sp. _glycines_) 

has been described as the causal pathogen in North America and _F. 

tucumaniae_ in South America. Phylogenetic evidence indicates the 2 

SDS pathogens do not share a most recent common ancestor, but appear 

to have evolutionary origins in the southern hemisphere since they 

are deeply nested within a South American clade of the _F. solani_ 

species complex. The fungi cannot be isolated from tissue above the 

soil line. Foliar symptoms are thought to be the result of a 

fungus-produced plant toxin.



It is suggested that any stress factor (biological, mechanical, or 

environmental) may magnify SDS symptom expression and cause 

SDS-affected plants to deteriorate earlier. In particular, Soybean 

cyst nematode (SCN), although not required for severe SDS to occur, 

is reported to exacerbate foliar symptoms and lead to early and 

severe SDS, if present at sufficient levels. Other soybean pathogens 

affecting leaves, roots, or stems are being studied for a potential 

role in SDS development.





Pictures



Links

- Mod.DHA]



2005

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Sudden death syndrome, soybean - USA (KY) 20050811.2350

2004

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Sudden death syndrome, soybean - Argentina 20040824.2357

2003

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Sudden death syndrome, soybean - Argentina 20030412.0886

Sudden death syndrome, soybean - USA (MN) 20030328.0776

2002

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Sudden death syndrome, soybean - USA (DE & MD) 20020710.4721

2000

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Soybean Fusarium infection, improved detection 20000920.1622

Soybean crop deaths - USA (Midwest) 20000827.1431]

...................................dha/mj/dk