IPM Pest Information Pages
Sudden Death Syndrome: Kentucky Soybean IPM
Sudden Death Syndrome
Sudden death syndrome (SDS) usually develops in "hot spots"
in a field and then progresses to
the remainder of the field. Affected plants develop
symptoms about the mid pod-fill stage of
development. Symptoms get progressively worse until the plants
Foliar symptoms will first appear as random, irregularly
shaped yellow blotches between the veins
of leaves. The blotches can start at any level in the
canopy of plants. As the disease progresses,
blotches run together and tissue between the veins dies,
but the veins remain green. Diseased
leaves may be distinctly curled due to excessive drying of
diseased tissue. Infected leaflets drop
from plants, but the leaf petioles usually remain attached
to the plant. Severe defoliation in the
early to mid-reproductive stages may be accompanied by
flower and pod abortion and dropping of
developing pods. Fully expanded pods, although they may
ripen prematurely, rarely fall off the
In addition to foliar symptoms, plants with sudden death
syndrome (SDS) will also show
characteristic symptoms of the roots and stems. Root
symptoms will be present before foliar
symptoms and appear as a general deterioration of taproots
and lateral roots. Nitrogen-fixing
nodules, present on the soybean roots, deteriorate and are
non-functional. The internal portion of
affected taproots will turn a milky gray-brown. This
general discoloration will extend up the stem
for several nodes, but the stem core remains a healthy
color of white.
SDS appears to be most common in fields with high soil
fertility and a soybean cyst nematode problem.
Sudden death syndrome (SDS) is caused by a strain of the
common soil fungus Fusarium solani (FS-A). Although FS-A is the primary organism associated
with SDS, other pathogens may also
be involved in disease development.
SDS symptoms are the result of root infections by FS-A.
The fungus cannot be isolated from
plant tissue above the soil line, which suggests that
foliar symptoms may be the result of a fungus-produced toxin. The fact that plants occasionally recover
after showing earlier foliar symptoms
suggests toxin action, however, any toxin's role in SDS
development has not yet been proven.
Researchers in Mississippi confirmed a link between soil
moisture and SDS. They found that root
infection by FS-A was highest and SDS more severe under
conditions of continuous, high soil
moisture during the early vegetative stages of crop
References and Additional Information
- IPM-3 Kentucky IPM Manual for Soybeans
- PPA-10b Kentucky Plant Disease Management Guide for Soybean
by D.E. Hershman, Extension
- PPA-37 Soybean Sudden Death Syndrome in Kentucky by Don E.
Hershman, Extension Plant
- Compendium of Soybean Diseases, J.B. Sinclair and P. A.
Backman (The American
Phytopathological Society Press)