Volume
5 Issue 7
July 1, 2008
Crop Health Studies: Effect of Fungicides on
Soybean Plant Health /
Yield in Northwest MN
Soybean leaf rust was first detected in the US in
2004. Fungicides will help to control leaf rust. In the mean time,
fungicides were promoted for their overall benefit through enhancing
plant health, even in the absence of disease. As a result,
replicated field trials were conducted to determine if any benefits
from fungicide use on soybean would translate into yield increases
within the region. This study was designed to determine whether
benefits from applying Headline (pyraclostrobin) or Folicur (tebuconazol)
fungicides at the R1 and R3 stage would promote “plant health” and
possibly result in increased yields for growers in northwest
Minnesota.
In general, no visual differences in the treatments were
observed. At the northern location in 2006, control plots appeared
to lose their leaves quicker, however defoliation estimates at the
end of August were not significantly different between treatments.
 Yield
results do not indicate a statistically significant yield increase
occurred from applying fungicides at either growth stage or at any
location during the two years that trials were conducted (Table
1).
In 2006, overall yields were lower at the Kragnes site when
compared to the other locations. This difference may be the result
of two minor hail events which occurred in late August and mid
September at the Kragnes site. Yields at Shelly were suppressed in
2007 due to excessive wet soils which delayed development in some
plots.
Soybean aphids reached treatable levels at southern locations in
2006 and were controlled with an insecticide application. When
aphids were treated, all plots were treated similarly. Aphids did
not require treatment in 2007 at any of the sites.
From NW regional studies conducted between 2004 - 2007, which
includes trials conducted by NDSU, we conclude that foliar
fungicides, applied to soybeans in the absence of infections of
foliar diseases, did not produce statistically significant yield
increases. Other replicated trials conducted in southern locations
of Minnesota have produced similar results. To see the results of
these and other trials from southeast and southwest Minnesota, go
to:
http://www.soybeans.umn.edu/regional/Southeast/index.htm
http://swroc.cfans.umn.edu/SWMNPEST/swmnpest.htm
Do we need to use Foliar fungicides in northwest Minnesota or
North Dakota? Probably not, but there could be exceptions. If you
are still interested in trying them, ALWAYS leave check strips that
would provide a valid comparison, not just untreated areas on field
edges. What about for soybean rust control? In the event that we
experience the arrival of Soybean Rust spores, the decision to use
fungicides will depend on growth stage of the crop when rust spores
arrive. If the crop has progressed past R6, then fungicides would
not be needed.
This project was funded by the Minnesota
Soybean Research
and Promotion Council.
Phillip Glogoza
Extension Educator, Crops
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