|
Des Moines, Iowa
August 23, 2001
Soybean growers across the South
and much of the Midwest may be seeing signs of sudden death
syndrome (SDS), a soil-borne disease that infects soybean fields
and cuts into yields. Checking for the disease now - in August
and September - can help growers build a plan of defense against
the disease next year.
According to Steve Butzen, agronomy information specialist with
Pioneer Hi-Bred International,
Inc., growers can minimize the potential for soybean yield
reduction from SDS in high-risk fields by selecting tolerant
varieties and following good management practices.
"By taking the time to manage SDS-prone areas, you can improve
your chances of successfully growing soybeans in potential risk
areas," Butzen says. "The key is understanding how the problem
can occur and then doing your best to manage against it."
Sudden death syndrome is most common when soybeans are exposed
to cool, moist soils early in the growing season. Early-planted
soybeans are often at risk. Soil that is compacted and poorly
drained also contributes to the problem.
SDS attacks soybean roots early in the growing season. The
Fusarium solani fungus that causes SDS survives in crop debris
in the soil. The organism enters roots through wounds caused by
soybean cyst nematode (SCN), insect feeding or mechanical
injury. A toxin produced by the fungus eventually moves through
the plant, causing above-ground symptoms, including yellow or
brown leaves with green veins, premature leaf drop, flower and
pod abortion and lack of pod fill.
Leaf symptoms of SDS are similar to those of brown stem rot
(BSR) and stem canker. To distinguish SDS from the other two
diseases, first examine the outside of a stem. Brownish-black
sunken lesions are signs of stem canker. If no lesions are
present, split the bottom eight inches of the stalk. The pith or
inner core of the stem will be white, and the surrounding cortex
will be grayish brown if SDS has infected the plant. In
contrast, BSR demonstrates dark-brown pith with a
green cortex.
Butzen recommends growers scout fields in August and September
to determine the extent of the problem. Identify suspect plants
based on leaf and whole-plant symptoms and then check stems and
roots to distinguish SDS from other soybean diseases. While SDS
is a difficult disease to manage, there are several varietal and
cultural practices that can help minimize damage to soybeans in
coming seasons:
- Plant at-risk areas to
tolerant soybeans. A number of new Pioneer® brand soybean
varieties demonstrate improved SDS tolerance ratings.
- Don't count on rotation as a
management solution. Rotation has not proven particularly
helpful because the causal organism can persist in the soil
for many years.
- Avoid planting soybeans early.
Early planting can put soybeans at greatest risk of SDS
infection, which occurs when temperatures are lower than 60 to
65°F.
Improve field drainage and work through compacted areas to
reduce infection by the SDS fungus.
- Evaluate tillage systems. High
crop residue levels result in colder, wetter seedbeds in the
spring. Disking or ridge tilling may help reduce the risk of
SDS.
- Work to eliminate additional
environmental stresses, including herbicide stress, nutrient
deficiencies, high pH and the presence of soybean cyst
nematode.
For more information about sudden
death syndrome or SDS management practices, contact your local
provider of Pioneer products.
Pioneer Hi-Bred International,
Inc., a DuPont company, is
the world's leading developer and supplier of advanced plant
genetics to farmers worldwide. With headquarters in Des Moines,
Iowa, Pioneer develops, produces and markets a full line of
top-quality seeds and forage and grain additives and provides
services to customers in nearly 70 countries. DuPont is a
science company, delivering science-based solutions that make a
difference in people's lives in food and nutrition, health care,
apparel, home and construction, electronics and transportation.
Company news release
N3760
|
