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Determining Fungicide Needs in Corn
By
Laura Skillman
PRINCETON, Ky., (June 20, 2007) – Questions about the need for
and possible advantages of using fungicides on corn arise every
year, but with the upswing in additional corn acres this year,
more growers are likely searching for answers.
“The principal diseases that might justify a fungicide treatment
in some fields are gray leaf spot and northern leaf blight,”
said Paul Vincelli, plant pathologist with the University of
Kentucky College of Agriculture. “Both of these are caused by
fungi that overwinter in corn residues of leaf blades and
sheaths, so they are naturally more severe when corn follows
corn under conservation tillage.”
Unfortunately, there is no formula for deciding whether a
fungicide application to field corn will provide an economic
return. Producers must think in terms of probability, just like
rolling a set of dice. There are many uncertainties that need to
be addressed with more field research. However, Vincelli said,
as more information is sought through research trials, it is
probably useful to consider the experiences researchers and
producers have had with fungicide use on soybeans. There are
many similarities between soybean fungicides and the use of
fungicides on corn.
In soybeans, yields are enhanced about 60 percent of the time
with the use of fungicides, he said, but it’s only profitable 28
percent of the time. Farmers must decide if that is often enough
to consider spraying a soybean field.
“I suspect the results in corn are going to be similar,”
Vincelli said. “In soybeans we don’t have guidelines when
deciding whether a particular field would benefit. In corn the
situation isn’t quite so dire.”
Several factors increase the likelihood of disease problems.
These include growing a variety susceptible to gray leaf spot or
leaf blight, growing continuous corn or no till corn, late
planting, irrigation, disease activity at tasseling and
disease-favorable weather. The more risk factors that apply to
producers’ fields, the more likely they are to have an
economical yield increase for fungicide in corn. High-yield
potential and high-value specialty corn also increases the
likelihood of a positive economic return from fungicide use.
“My recommendation is if you are interested in trying a
fungicide, try it out,” Vincelli said. “But always, always leave
a check strip for comparison. Then put a pencil to the economics
after you harvest both strips.”
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Contact: Paul Vincelli, 859-257-7445, ext. 80722
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of Agriculture, through its land-grant mission, reaches across
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