New Prescription for
Soybean Cyst Nematode Plague
With recent studies at Iowa State University estimating
that nearly 90 percent of the state’s soybean acreage is now infested
with soybean cyst nematode (SCN), most producers are fighting an up-hill
battle with the cancerous-like worm whether they know it or not.
SCN attacks beans at the root structure, often causing critical damage
before symptoms surface above ground. The feeding worms stunt root development,
reduce water absorption, interfere with nodulation by nitrogen-fixing
bacteria, and siphon nutrients off the plant. Yet, many times yield
reductions are the first indication that this "silent partner"
exists. Even then, other factors such as poor drainage or fertility
problems often are mistakenly diagnosed. SCN is difficult to identify
and even more difficult to control.
With the widespread growth of SCN across every bean-producing region
in the country, one thing is readily apparent – conventional efforts
to control the problem are not working.
Mobility and environmental tolerability make SCN very
difficult to combat. In the absence of a host plant, the cyst or body
wall from the female nematode protects the eggs inside and can allow
them to persist in the soil for 10 or more years. In addition, any object
that comes in contact with the soil of an infested field has the potential
to spread the cyst to a new location – whether it be farm equipment,
pant cuffs, boots, livestock, wildlife, or water runoff. "Critical
Mass," or the presence of sufficient nematodes in the soil to noticeably
reduce soybean yields, can occur very quickly. In 1997 alone, the Iowa
Soybean Association estimates that SCN robbed soybean producers of 209
million bushels. That number is climbing, but help may be on the way.
In mid-December 1998, Mark Seed Company announced the exclusive release
of a patent-pending technology that reduces SCN populations. The Perry,
Iowa-based company’s proprietary Cyst Tech® process has proven
effective at controlling SCN in the soil without forcing race mutation,
which has been the primary downfall of today’s most common defense
approach – SCN resistant seed varieties.
Combating Race Shifting
Sixteen races of SCN are currently recognized, with race three by far
the most dominant type. Some estimate race three represents as much
as 90 percent of the total SCN population. Therefore, it’s no
coincidence that the majority of resistant seeds target the race three
nematode. In fact, while products exist for the other races, to date
none have been able to significantly reduce populations while maintaining
satisfactory production yields.
Race three resistant seeds have proven effective at decreasing populations
during the first year.
However, with continued use much of the cyst population
mutates to different races and the resistant seeds no longer remain
effective. Because the root feeding worm can complete its life cycle
in as little as four weeks under ideal conditions a race shift can occur
very quickly – many times as soon as the second growing cycle.
"The one thing that we absolutely want to avoid is race shift (or
a change in the SCN race structure)," says Tim Todd, a nematologist
with Kansas State University Extension. "That would be very bad
because of the potential for subsequent yield loss in formerly resistant
cultivars."
The Conventional Solution
In the past, race shifting has been countered by a
method that alternates planting of resistant seeds and susceptible seeds
around two-year corn rotations. Producers plant a resistant seed the
first year, followed by two years of corn and then a year of SCN susceptible
beans.
According to field studies, this approach slows the increase of SCN
population growth. However, population reductions during the resistant
seed planting cycle and the corn rotation do not offset the population
gains surrendered by the susceptible seed. The trend line continues
to climb. SCN populations eventually become unmanageable, ultimately
leading to production declines.
"Because the race resistant seed approach is race selective, it
will never serve as an effective long-term solution," says Mark
Terpstra, president of Mark Seed Company. "You cannot keep up with
the genetic evolution of these pests. We tried a similar approach with
Phytophthora. It didn’t work because we just kept finding new
stands.
The solution must control population growth and race." he continued.
The Cyst Tech® Solution
Cyst Tech® features a proprietary process that controls cyst nematode
population, stifles race mutation and maintains top yields in SCN infested
fields.
"Our new technology is so unique because it is geared toward various
levels of cyst infestations, and it adapts to ramifications of prior
attempts to control SCN." explains Terpstra.
"Cyst Tech® is a two-fold process, using a "Level A"
product to combat race shifting and a "Level B" product to
control population."
According to Terpstra, the Cyst Tech® process incorporates the two
solutions Cyst Tech® A then rotate with Cyst Tech® B, or a one
year corn rotation in between. If the producer last used a resistant
seed in the field, Cyst Tech® Level A product would be prescribed
first to bring the SCN population races in line. One year of corn then
would be planted, followed by the Level B product to reduce SCN population.
If a susceptible seed was last planted, Level B would be used to reduce
population and then Level A would be applied to control race after the
corn cycle.
Terpstra concedes that no current product or process can completely
eliminate the presence of SCN. However, he points out that Cyst Tech®
process is a cost-effective way to achieve immediate and sustainable
SCN population reduction, while maintaining strong crop yields.
For more information about SCN
and Cyst Tech® process, producers can contact Mark Terpstra at Mark
Seed Company at (800) 383-6275.
Top
CTA Planting Guidelines
1. Plant Cyst Tech® Level A on soil that has either a history of
a SCN resistant soybean program or a Cyst Tech® Level B soybean
that has been planted previously.
2. Cyst Tech® Level A will manifest a cyst nematode race shift back
to a controllable race allowing for a reduction in SCN when combined
with a rotation of Cyst Tech® Level B.
3. Cyst Tech® Level A will not force race mutation common with cyst
nematode resistant varieties.
4. Improved yields and lower cyst counts will result from rotating Cyst
Tech® Level A and Cyst Tech® Level B over the years.
We recommend steps 5 & 6 also to increase your soybean yields.
5. Spray Warrior ® insecticide 5 days after planting.
6. Apply Warrior ® at the first sign of soybean aphids.
CTB Planting Guidelines
1. Plant Cyst Tech® Level B on soil that has either had history
of a susceptible soybean or a Cyst Tech® Level A soybean that has
been previously planted.
2. Cyst Tech® Level B substantially reduces the SCN population while
improving yields when combined with a rotation of Cyst Tech® Level
A where previously planted.
3. Improved yields and lower cyst counts will result from rotating Cyst
Tech® Level B and Cyst Tech® Level A over the years.
4. Do not plant Cyst Tech ® Level B followed by Cyst Tech® Level
B.
We recommend steps 5 & 6 also to increase your soybean yields.
5. Spray Warrior ® insecticide 5 days after planting.
6. Apply Warrior ® at the first sign of soybean aphids.
