Soybean Sudden Death Syndrome
Sudden death syndrome (SDS) is the common name for a root-rot of soybean caused by the fungus Fusarium solani f.sp. glycine. The disease was first found in North Carolina in 2001, although it may have been present earlier (Figure 1). Yield loss in 2001 was negligible. The likelihood that major yield loses from SDS will occur in North Carolina is unclear, but SDS is a potentially serious disease. Periodically this disease has been a problem in the mid-south and mid-west since the 1980's. Most years the disease is of minor importance. In years when disease symptoms are widespread and apparently severe, soybean yields are generally excellent. The name "sudden death" refers to the early defoliation and death of the soybean plant. The common name stems from the fact that in wet years, foliar symptoms seem to spread rapidly through a field at or after the pod filling stage. Disease is usually more severe in high yield environments. Sudden death syndrome is often associated with the soybean cyst nematode, Heterodera glycines. See Soybean Disease Information Note #1 for more information.
Foliar symptoms of soybean sudden death syndrome resemble those caused
by several other plant pathogens and or damage from certain insects (Figures
2 & 3). Red crown rot (black root rot), phytophthora root rot, charcoal
rot, stem canker, brown stem rot, southern blight, and occasionally, damage
from dectes stem borer (an insect) may also cause leaf symptoms that resemble
SDS (see Soybean
Disease Information Note No. 5 - Identification and Management of Mid-to-Late
Season Soybean Stem and Root Rots, or the Soybean
Disease Atlas). The symptoms associated with red crown rot, caused
by Cylindrocladium parasiticum (the same fungus causes CBR in peanut),
are virtually identical to those found with sudden death syndrome caused
by F. solani.
As mentioned earlier, a number of pathogens cause symptoms that resemble SDS. Red crown rot, in particular, has symptoms that are virtually identical to SDS. Often it will be necessary to have the fungus isolated to be certain of the cause. Plant and soil samples can be sent to the plant disease and insect clinic through your North Carolina Cooperative Extension Service County Agent.
Disease Cycle and Epidemiology
syndrome is caused by the soil-inhabiting fungus Fusarium solani
f.sp. glycine The fungus survives in the soil for numerous years
and may be able to increase on other hosts. Crop rotation does not seem
to affect disease severity, and sudden death syndrome has occurred following
corn or cotton crops. Suppression of soybean cyst nematode through crop
rotation or the use of cyst resistant soybean varieties may result in
less disease. Infection of soybean roots by F. solani probably
takes place shortly after soybean emergence. Wounds or changes in plant
physiology caused by infection by plant-parasitic nematodes may increase
the severity of SDS. Disease development is favored by high soil moisture.
Symptom development may progress rapidly following cool weather. The fungus
survives in decayed plant tissue and soil after the plant dies.
for management of SDS is based on data developed in other states. Soybean
varieties with moderate-to-high levels of resistance to SDS are available
(Table 1). Growers are advised to check literature provided by their seed
supplier for information on disease resistance. Varieties resistant to
SDS should be considered in fields known to be affected by this disease.
In choosing a variety, however, be certain that it has resistance to pathogens
known to be present such as Phytophthora sojae, cyst or root-knot nematodes.
Many new varieties and especially varieties in later maturity groups have
not been evaluated for resistance to this disease.
syndrome tends to be more severe in fields under reduced tillage regimes.
Late planting, as occurs with double cropping small grains and soybean
or the use of early maturing varieties may also suppress disease development.
Table 1. Varieties moderately-to-highly resistant* to soybean sudden death syndrome(SDS) caused by Fusarium solani f.sp. glycine.
* Most of this information was obtained from the seed company catalogs and is based on limited trials conducted by University and company personnel. Many soybean varieties in maturity groups V-VIII have not been rated for this disease.
For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service personnel.