Specialist Notes Increased Foliar Fungicide Use On Corn And Soybeans
URBANA, ILL.
Foliar fungicide use on corn and soybean in
Illinois has increased considerably in the
last few years. The primary fungicide class
being applied to these crops is known as “strobilurins”,
notes Carl Bradley, University of Illinois
Extension plant pathologist.
These fungicides are generally considered to
be broad spectrum (effective against many fungal
organisms) and preventative (applied prior to
or at the beginning stages of disease). Examples
of strobilurin fungicides are Headline and
Quadris.
Bradley has coordinated corn and soybean
fungicide trials across Illinois the past two growing
seasons. Results were presented at the University
of Illinois Corn and Soybean Classics
held across the state last month.
In soybean, Quadris and Headline were evaluated
and compared to untreated controls at 7 locations
in 2008. Results showed a yield
response range from 8 to 12 bushels per acre,
with the average response to a fungicide at 2.6
bushels per acre.
In 2007, the study was conducted at 11 sites
and the yield response range was 15 to 12
bushels per acre, with the average response to a
fungicide at 0.5 bushel per acre.
The amount of yield increase needed to make
a fungicide application profitable depends upon
the cost of the fungicide, the application cost,
and the contracted price of the crop. The cost of
the fungicide plus application can range from
$22 to $28 per acre.
For soybean contracted at $8, $10, or $12 per
bushel, a grower would need a return of approximately
3, 2½, or 2 bushels per acre from
the fungicide to “break even”.
Bradley notes that in the soybean fungicide
trials, a fungicide application would have been
profitable 40 percent and 55 percent of the time
in 2007 and 2008, respectively, assuming that
2½ bushels per acre return is needed.
Deciding to apply a foliar fungicide to soybean
requires evaluating several factors. Some of
these are:
• Previous crop. If the same crop is planted
back-to-back, then the risk of some foliar diseases
increases.
• Variety susceptibility. Check the company
rating for susceptibility to diseases such as frogeye
leaf spot. Varieties with greater susceptibility
to foliar diseases tend to have larger yield
response to foliar fungicides.
• Weather and environment. Foliar diseases
tend to thrive more under wet and humid conditions.
• Disease observations. Crop scouting or
monitoring is always important.
Bradley commented that the above-mentioned
research has been supported by funding from
the Illinois Soybean Association. Δ