Michigan State University Extension
Michigan Soybean Information - FACT9705
11/16/00
Soybeans - Sudden Death Syndrome
List of files and visuals associated with this text.
Soybean Facts Winter 1997
Michigan State University Extension
This research and fact sheet funded by Michigan
Soybean Promotion Committee Making Your Checkoff Pay Off
L.P. Hart
Department of Botany and Plant Pathology
Michigan State University
Sudden Death Syndrome (SDS) is a fungal disease, not
yet positively identified in Michigan, but which
probably occurs in many areas of the state.
Special Observations
1. SDS becomes evident after flowering, most often
after the pod-fill stage.
2. SDS generally appears in late July and early
August, although delayed planting does reduce
disease development.
3. Pay special attention to early planted fields
when scouting.
4. Also watch closely fields that are flat, fertile
and expected to have high yields.
Visual Symptoms
SDS symptoms are fairly easy to identify. Leaves on
infected plants first have scattered yellow or white
spots between leaf veins. These spots start to die
and enlarge to form brown streaks between the veins
(interveinal necrosis). Only mid-vein and major
lateral veins remain green. Eventually, infected
leaves drop but petioles remain on the stem.
Diseased plants with SDS are easily pulled out of
the ground because the taproots and lateral roots
have deteriorated due to root rot. The root cortex
will be a light gray-brown and the discoloration may
extend up into the stem. If infections are severe
during the early reproductive stage, flower and pod
abortion may occur.(Vis. 1)
(Vis. 2)
(Vis. 3)
SDS Resembles Brown Root Rot and Stem Canker
It is possible to mistake two other common soybean
diseases, the foliar-type brown stem rot (BSR) and
stem canker, for sudden death syndrome because these
diseases have similar leaf symptoms.
Differences include:
SDS - symptoms on both leaves and roots, light
graybrown discoloration in the vascular tissue, and
root rot makes soybean plants easy to pull
BSR - brown discoloration in the main stem that is
limited to the pith
Stem Canker - brown canker on the main stem and
stems become brittle
Recent reports suggest that SDS is commonly associated
with Soybean Cyst Nematode (SCN). SCN occurs in many
counties throughout Michigan. So special attention to SDS
should be given to these fields.
Summary
Though not previously identified in Michigan, it is
likely some fields may have a history of SDS. Michigan
has many flat, fertile, high producing fields. Some of
these fields have a history of BSR and/or SCN. As you
scout your soybean fields, please note any special
symptoms described for SDS and report them to your County
MSUE or your agribusiness consultant. Then ask them to
contact Dr. L.P. Hart at MSU Department of Botany and
Plant Pathology or the Michigan Soybean Promotion
Committee to help in positive identification of your
troubled field.
SDS, A Historical Perspective
Sudden Death Syndrome of soybeans was observed in
Arkansas in 1971, but wasn't considered economically
significant until 1982 when it caused yield losses
of 25% in up to 10% of the total soybean acreage in
Arkansas. Since then, SDS has been observed in most
states with large soybean acreage, including Indiana,
Illinois, Ohio, Missouri and Iowa. The plant pathogen
initially thought to be related to isolates of F. solani
f. sp. phaseoli that cause root rot, recent reports
suggest SDS strains are biologically distinct.
Preliminary Research Results
Once SDS has been identified it appears to be only a
matter of time before it gains economic significance.
Yield losses of 20-80% may occur, depending on the
variety and the timing of symptom appearance. Symptoms
occurring at early pod fill (before stage R5) result in
more damage and yield reduction than when symptoms occur
later. Yield reduction is reportedly due to pod abortion,
lack of pod fill and low test weight. Information is
inconclusive on the role of varieties and environment on
disease initiation, development and spread. However,
there are varietal differences, and recent comparisons
between field and greenhouse varietal tests indicate that
greenhouse screening may be a reliable indicator of
variety susceptibility or resistance. In Arkansas,
varieties resistant to the soybean cyst nematode
developed SDS at a slower rate than susceptible
cultivars. Also, disease symptoms appeared later in group
IV varieties when compared to group V, VI and VII
varieties. Thus, group I, II and III varieties may
have less disease because they mature earlier. Late
planting has also been reported to reduce disease
development.
Copies of the Soybean Research Fact Sheet are available
from:
Michigan Soybean Promotion Committee
http://www.michigansoybean.org
MSUE County Office
http://www.msue.msu.edu/msue/ctyentpg/
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