Sudden Death Syndrome
Photo Courtesy of:
http://www.ent.iastate.edu/ipm/icm/1999/8-9-1999/isdsleaflet.html
Last updated by
Nick Dolezal
on February 10, 2002
Common Names of Sudden Death Syndrome:
-SDS
Causal Agent:
Species:
Fusarium solani
f. sp. glycines
Class:
Fungi
Order:
Ascomycetes
Host Range:
Here are some of the alternate crops, ornamentals, and weeds that Fusarium
can survive on:
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Geographical Range:
Sudden Death Syndrome has been a problem in southern states such as Kansas, Mississippi, Tennessee, and Iowa. Lately, the disease has spread northward into Wisconsin and Minnesota.
Symptoms:
As seen in the photo at the top of this page, SDS can be very detrimental to a soybean crop. Initially, SDS appears as yellow spots on a leaf surface. Eventually, these spots will become necrotic leaving the veins intact. The disease will then spread into the veins and then cause leaf abscission. If infection occurs at the right time, flowers and pods may be aborted. SDS can be easily diagnosed by splitting the stem and looking for browning of the vascular tissues.
Dissemination:
Basically, anything that can move soil, can transport Fusarium solani. Also, infected plant debris which is moved from field to field may spread the disease.
Disease Cycle:
There is some information known about the complete disease cycle of SDS at this time. Evidence has been documented that shows Fusarium enters the root of a soybean plant from the soil as a result from root injury caused by mechanical means, insects, or nematodes. This is why SDS is more common in fields that contain Soybean Cyst Nematode SCN. It is widely believed that once the disease has entered the vascular tissue it transports toxins to the upper portions of the plant causing the symptoms of SDS. The fungus survives in the soil and on plant tissue as mycelium and spores.
Control Measures:
There
is no complete control of SDS available. There are some soybean varieties
that show partial resistance however, no completely resistant varieties
are available. Fungicides or nematicides don't rid the pathogen enough
to have an effect. The best methods of control are cultural.
Use the partial resistant varieties, as well as rotate the crops planted
on a piece of ground often. It is recommended that different maturities
of soybeans are planted over a soil during normal crop rotation as to break
the fungus life cycle. Reducing moisture levels in the field with
good drainage can aid in suppressing the pathogen. Also, controlling
SCN levels, as described in profile 1, will
help in reducing the infection of SDS.
Recent Research-Summary:
Related Journal Article:
Sanogo, S. Yang, X.B. Jun, 2001. Relation
of sand content, pH, and potassium and phosphorus nutrition to the development
of sudden death syndrome in soybean.
Canadian Phytopathological
Society.
23:174-180.
The reason for the study performed here was to find out the relationship of each of the variables tested against SDS occurrence. Soybeans we subject to increased of decreased levels of the variables listed above. Then Fusarium solani was introduced to the plants. The results showed that SDS increased almost proportionately with an increase in soil sand content. Also, the occurrence of SDS increased with an increase in pH. Higher calcium levels increased severity of SDS while higher potassium chloride decreased levels. other forms of potassium increased SDS levels. this study was good in that it provided insight on how farmers might be able to control SDS in the future.
Sources:
Agrios, George N. 1997. Plant Pathology 4 ed. Academic Press.
pp. 352-354.
University of Illinois. Extension Website.
http://www.ag.uiu.edu/~vista/abstracts/a512.html
University of Minnesota. Extension Web site.
http://www.soybeans.umn.edu/crop/diseases/sudden_death.htm
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