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Agronomy Day 2009

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Tour B

Aerial Fungicide Applications to Corn for Disease Control

Scott Bretthauer
Scott Bretthauer
Department of Agricultural
and Biological Engineering
Carl A. Bradley
Carl A. Bradley
Assistant Professor
Department of Crop Sciences

Agricultural aircraft are an accurate and efficient way of applying foliar fungicides on corn and other
crops. The advantages of using an aircraft for these applications include speed, the lack of disturbance
and damage to the crop, and the ability to work when the ground is wet. While the actual acres
sprayed in a day depend on aircraft size, field size, and ferry distance, a single aircraft can treat on
average between 1,500 and 2,000 acres in a day. Fixed-wing aircraft and helicopters can both be used,
and the aircraft are set up to provide a uniform spray pattern by placing nozzles out of zones of
turbulence created during flight. Creating the correct droplet size is important for fungicide
applications, and agricultural aircraft create a narrow spray droplet spectrum which allows them to
provide coverage and canopy penetration at low spray application rates. For aerial applications,
droplet size is controlled by the nozzle type, orifice size, operating pressure, aircraft speed, and the
angle of nozzle deflection. Agricultural aircraft are tested at Operation S.A.F.E. fly-ins to ensure an
aircraft is setup correctly. At a fly-in clinic, an aerial applicator can view his spray pattern to make
sure it is uniform, determine his effective swath width, and examine the spray droplet size created by
his aircraft to ensure both an effective and safe application.

Aerial application of a fungicide to a corn field
Aerial application of a fungicide to a corn field

Disease control should be the primary reason a foliar fungicide is applied to corn.  Fungicide decisions can be made based on disease risk and scouting observations.  The risk of disease in a corn field can increase when certain factor are present.  Some of these factors are: previous crop, hybrid susceptibility, planting date, and weather.  When corn is planted back into a field that was corn the previous year, the risk for disease increases, especially when much of the corn residue is left on the soil surface.  It is important to choose hybrids with strong resistance to foliar diseases, but unfortunately this is not always possible.  When planting hybrids that are more susceptible to foliar diseases, the risk of disease does increase.  Research has shown that corn fields planted later than average may have an increased risk of disease.  This may be due, in part, to larger levels of spores of the fungal pathogens being present later in the year, as well as the crop not being fully-developed when infection occurs.  Environment is often the limiting factor on if foliar diseases occur.  In general, weather conditions that keep leaves wet for an extended period of time (high relative humidity, frequent rainfall, cloudy weather, etc.) are favorable for foliar diseases.  University of Illinois foliar fungicide trials conducted at eight different Illinois locations in 2008 indicated that high yield responses occurred only at locations with higher levels of disease pressure.  Fungicide applications to corn when disease pressure is absent or low is generally inconsistent in providing “yield bumps”; thus, it is important to focus on disease control when making fungicide application decisions.

Yield response of corn to foliar fungicides with regard
Yield response of corn to foliar fungicides with regard
to disease pressure at eight Illinois locations in 2008.

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