Urbana Champaign, Illinois
April 9, 2009
Source:
The
Bulletin No. 3/April 10, 2009, University of Illinois
Extension
Use of fungicide seed treatments
on soybean seed is not currently the norm for Illinois
producers, but it has increased in the past few years. Beginning
with the 2009 season, seed of some varieties (such as all
Monsanto Roundup Ready 2 Yield varieties) are being sold
pretreated with fungicide treatments, which eliminates the
producer's input on whether a fungicide seed treatment is needed
and, if so, which product(s) to use.
For those who still have a choice, there are some factors to
consider when deciding to use fungicide seed treatments on
soybean. In general, there are two potential reasons to treat
soybean seeds with a fungicide: if poor-quality seed is being
planted, and to protect against seedling diseases.
Poor-quality seed. It is always recommended that the
highest-quality seed be planted, but this is not always
possible. Fungicide seed treatments may be able to help improve
the stand establishment of a variety with poor-quality seed.
This is especially true if the poor quality is due to infection
by a fungal seedborne pathogen. If it is due to mechanical
damage, a fungicide seed treatment will not increase the
germination rate, but it may help in providing a more uniform
stand, which could (but doesn't always) translate into greater
yields.
In 2008, a field research trial was conducted at Urbana to
evaluate the effect of fungicide seed treatments on a soybean
seed lot with a low germination rate. In this trial, fungicide
seed treatments did improve the yield compared to the untreated
check. In addition, some seeds were run through the seed treater
without being treated with a fungicide to determine whether
running the treater had a detrimental effect. In this trial,
there was no significant difference between untreated seed and
seed run through the treater with no fungicide applied.
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Effect of fungicide seed
treatments on poor-quality soybean seed at Urbana,
Illinois, in 2008. |
Protection against seedling
diseases. Seedling diseases of soybean can be caused by
pathogens such as Pythium, Phytophthora, Rhizoctonia, and
Fusarium. In some cases, a complex of these pathogens may affect
soybean seedlings. Fungicide seed treatments can be effective in
protecting seeds and seedlings from these pathogens for a short
period of time, which may allow the seedlings to become
established and be productive plants. The risk of being affected
by seedling diseases may increase when planting early (April to
early May), when planting into a field with a history of
seedling disease problems, and when weather conducive for
seedling diseases (generally cool and wet) appears just after
planting. A summary of University of Illinois soybean seed
treatment trials conducted from 2001 to 2008 shows that the
average increase in yield obtained with a fungicide seed
treatment was 0.8 bu/A; however, the yield advantage became
greater when fields were planted earlier (late April to first
week of May).
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Summary of University of Illinois fungicide seed
treatment trials on soybean from 2001 to 2008 (trials
through 2006 conducted by Dr. Wayne Pedersen; 2007 and
2008 trials conducted by Dr. Carl Bradley). |
Which product(s) should I use? If
you decide to use a seed treatment on soybean, it is important
to use a product that provides broad-spectrum control of many
pathogens. The treatment should include one of the active
ingredients mefenoxam or metalaxyl, which provide some
protection against oomycete pathogens (i.e., Pythium and
Phytophthora). In addition, the treatment should contain at
least one other fungicide (fludioxonil, trifloxystrobin,
pyraclostrobin) that will provide broad-spectrum control against
Fusarium and Rhizoctonia.--Carl A. Bradley |
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