Ames, Iowa
April 20, 2009
Source:
Integrated
Crop Management News, Iowa State University
by X.B. Yang, Department of Plant Pathology
Seed treatment was not a major production issue ten years ago
because less than 3 percent of soybean planted in Iowa used seed
treatment. Now the number is more than 50 percent, according to
a survey. Such changes are associated with changes in soybean
production. Increased cost of seeds and early planting in spring
may be driving forces for such changes.
It is no question that seed treatments can increase yield in
fields where risk of seedling diseases are high, for example,
growers in Ohio routinely use seed treatment to prevent
Phytophthora damping off. Despite the greater demand for seed
treatment today, it is unknown if the majority (50% or more) of
Iowa soybean fields will see an economic return from treatments.
This is because of lower seedling disease risk in Iowa compared
to Ohio and because soybean plants have a greater ability to
grow over a large gap. Assessing the risk of seedling diseases
in particular fields before use of a seed treatment can provide
the producer needed protection while reducing production cost.
Why seed treatment
In Iowa, as well as elsewhere in the North Central Region, seed
treatments are mainly to protect seedling from damping off by
Phytophthora and Pythium. In some years Rhizoctonia and Fusarium
can be production problems to a few growers, both neither create
major problems.
When to treat seeds or effectiveness of seed treatments
Because in most seasons seedling diseases are not a general
problem and are unique problems to individual Iowa farmers,
producers should selectively use seed treatments in order to
reduce production cost. Below are specific cases where one
should use treated seeds.
1. When seed quality is
poor, such as last year. Seed treatment will not improve
germination rate, but will protect further stand loss.
Generally speaking, this year the seed quality has been
good. Seed quality has not been an issue.
2. Your fields have a history of severe damping off from
Phytophtora or Pythium and the coming spring is wet.
Phytophthora can cause damping off for some Iowa soybean
producers, especially in southern Iowa. However, if spring
is not wet, the disease will not be a problem. This also
applies to Pythium when soybeans are planted early. Pythium
is a cool temperature disease and is not a concern when
soybean is planted later in May or after.
3. Replanting. If replanting is needed, seed treatment is
insurance for a good stand. The lack of stand establishment
during germination is a sign of seedling disease in your
field. Using seed treatment is a must. However, insects such
as seed corn maggots sometimes cause seed rot. Make sure the
lack of soybean stand is from disease, not insect when you
replant.
4. Early planting. Early planting, planting before May, is
not a reason in itself for seed treatment. When soybean is
planted earlier, the soil is cool and seedling diseases
Pythium and Fusarium occur in cool soils. Past surveys of
these diseases indicate Fusarium only accounts for about 10
percent of seedling disease problems in Iowa.
Finally, many seed treatment has
multiple packaging which includes insecticide such as Cruiser.
Seed treatment with insecticide will not help aphid control, but
it may reduce first generation of bean leaf beetles if the
insect is a concern in your production.
XB Yang is a professor of plant pathology with responsibility in
research and extension. Yang can be contacted by email at
xbyang@iastate.edu or by
phone at (515) 294-8826.
This article was published originally on 4/13/2009 The
information contained within the article may or may not be up to
date depending on when you are accessing the information. |
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