Michigan State University Extension
Michigan Soybean Information - FACT9802
11/16/00
Management of Soybean Cyst Nematode in Michigan
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The soybean cyst nematode (SCN) is a major limiting factor
in Michigan soybean production. This pest was first
detected in Michigan in 1987. SCN now is known to be
present in 30 counties. It is currently estimated that 25%
- 30% of Michigan's soybean acres are infested with SCN.
SCN infestations result in poor stands, stunted plants,
yellow foliage and low bean yields. Losses can range from
5-90% of the yield potential. It is imperative for all
Michigan soybean growers to have a well-developed strategy
to avoid SCN problems or to minimize impacts if SCN is
already present.
Avoidance of SCN
The first line of defense against SCN is avoidance. All
Michigan growers should strive to avoid SCN infestations.
The best way to avoid SCN is to never plant a field to a
host crop more than one out of every three years. Rotating
soybeans with nonhost crops, particularly corn and small
grains, in the absence of SCN, minimizes the risk of SCN
problem development. Rotation, however, does not completely
eliminate risk. SCN has a relatively narrow host range. In
Michigan, it reproduces on soybeans, dry beans, snap beans
and peas.
SCN can be transported over long distances in soil
associated with crop transplants (e.g., tomato, strawberry,
ornamentals), on machinery, animals and with seed in the
form of soil peds. Because SCN occurs in the soil, it is
important to keep the movement of soil to a minimum. Fields
without SCN should always be worked and harvested before
infested fields. To minimize the spread of SCN, equipment
should always be washed free of soil after working
SCN-infested fields.
Nematode Monitoring
Monitoring for SCN is an essential part of nematode
management. All soybean fields in Michigan should be
routinely sampled for nematodes, preferably every fall
before soybeans are planted. At a minimum, soybean fields
should be sampled at least once every 3 years. SCN
management strategies must be based on the nematodes
detected in these samples. Early detection is critical to
avoid drastic yield losses and high population densities of
SCN. Sampling for plant-parasitic nematodes is described in
MSU AG Facts Bulletin E-2199, Detecting and Avoiding
Nematode Problems.
SCN Population Reduction
Nematode population reduction is the strategy used for
minimizing risks in fields infested with SCN. If SCN is
present, the objective in most situations is to reduce the
population density. This is done by growing nonhost crops,
maintaining good weed management, tillage, nematicide
applications or the use of SCN-resistant soybean varieties.
Crop Rotation. Two years of nonhost crops such as corn,
potatoes, small grains, sugar beets and most vegetables
will lower SCN numbers and reduce yield losses. Alfalfa and
red clover are very poor hosts of SCN. Dry beans, snap
beans and peas must be avoided. Population densities of SCN
will decline in the presence of nonhost crops. Occasionally
population declines are marginal particularly with corn. It
is difficult to predict how SCN populations will respond in
the presence of nonhost crops, and it is essential that
SCN-infested fields be resampled before soybeans are grown.
The duration nonhost crops should be grown before the next
soybean crop is dependent on the number of SCN eggs and
second-stage juveniles recovered from 100 cm3 of soil.
Weed Management. Weed problems are much greater in
SCN-infested fields than in non-infested fields. Good
management of weeds, water and soil fertility increases the
tolerance to SCN infection. Some weeds are hosts of SCN.
Purple deadnettle, henbit, field pennycress and
shepherd's-purse were found to support SCN in a study done
at Ohio State University. Growers should scout fields for
these winter annuals in the fall. If they are found in
fields infested with SCN, control is recommended.
Tillage. Reduced tillage systems can result in reductions
in SCN population densities compared to conventional
tillage. These results, however, vary from farm to farm and
are impacted by individual farming practices. Reduced
tillage will retard the within field spread of SCN. There
are no reports where reduced tillage resulted in increased
SCN damage, but these systems may result in the presence of
weeds that could serve as alternate hosts to SCN. Personal
communication with selected Michigan growers indicates that
symptoms due to SCN feeding are not as severe or widespread
in no-till or fields under reduced tillage.
Nematicides. A limited number of nematicides, such as Temik
15G, are registered for control of SCN in Michigan. In
general, the economics of nematicide use for control of SCN
under Michigan conditions has not been justified.
Resistant Varieties. SCN-resistant varieties are available
and should be an integral part of any SCN population
reduction program. In infested fields, SCN-resistant
cultivars yield 5-100% more than their susceptible
counterparts. Current resistant varieties are not adequate
for use in fields with extremely high population densities
of SCN.
SCN-resistant varieties generally have one of two sources
of resistance (Peking or PI 88788). In general, varieties
with the PI 88788 source of resistance have yielded best in
variety trials in Michigan and throughout North Central
States. Both private and public varieties are available
that are resistant to SCN. Please check with your seed
supplier for this information. It is recommended that
growers establish their own strip trials to evaluate
SCN-resistant soybean varieties on their farms. This is
important because varieties reported to be resistant to SCN
differ in their yield potentials and their degree of
resistance to the nematode. All on-farm strip trials should
include at least one variety susceptible to SCN for
comparison purposes.
Presently, because commercial lines have only one of two
potential sources of resistance, it is important to rotate
the sources of resistance as well as rotating crops.
Resistance to SCN may break down if one source of
resistance is grown too frequently on a site. Research
indicates that SCN will adapt in 2-4 years in the presence
of resistant varieties with the same source of resistance.
It is also important to occasionally include an
SCN-susceptible variety in the rotation if the population
density of SCN drops below detectable levels or is low
enough to allow profitable production of these cultivars.
Recommended Cropping Scheme
A nine-year cropping scheme is recommended for growers to
avoid SCN or to minimize its impact in infested fields.
This scheme integrates much of the information already
provided.
Year 1 Nonhost crop
Year 2 Nonhost crop
Year 3 Soybeans (PI 88788 resistance)
Year 4 Nonhost crop
Year 5 Nonhost crop
Year 6 Soybeans (Peking or other source of resistance)
Year 7 Nonhost crop
Year 8 Nonhost crop
Year 9 Soybeans (susceptible variety)
Michigan Soybean Cyst Nematode Distribution
(Vis. 1)
(Year of detection listed within the county. Note: To date
the Upper Peninsula has had no detection of SCN)
SOYBEAN FACTS
OCTOBER 2000
Management of Soybean Cyst Nematode in Michigan
F.W. Warner and G.W. Bird
Department of Entomology
Michigan State University
This research and fact sheet funded by
Michigan Soybean Promotion Committee
Putting Your Checkoff To Work
Michigan Soybean Promotion Committee
PO Box 287, Frankenmuth, MI 48734
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This file was generated from data base S1 on 11/16/00.
Data base S1 was last revised on 11/16/00.
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