Q&A: Real world experience with fungicides – Justin Brown, Ag Partners

Posted on March 22, 2016 in Forage Foundations
Justin Brown is an agronomist with Ag Partners Coop based in Goodhue, Minnesota.  He works with producers throughout southeast Minnesota and western Wisconsin.

What percentage of corn acres do you see treated with fungicide?
Currently, I only see 5 to 10 percent treated. However, our top producers of corn silage (yield) are leading the charge.

What percentage of alfalfa acres do you see treated?
About 5 percent.

What are the most popular products for each crop?

How do you decide which fungicide to use?
It needs to be a fungicide that is approved for that specific crop.  Then we look at the fungicide’s mode of action.  Each fungicide has different modes of action and we switch between brands based on the mode desired.

What application strategies are used?

  • Corn: Airplane, helicopter and ground applications
  • Alfalfa:  Ground sprayer

What is the approximate cost, including application?

  • Corn: $25 to 29 per acre
  • Alfalfa: $22 per acre

What benefits do manufacturers claim?

  • Corn silage: Higher yield and less disease
  • Alfalfa: Lower canopy leaf retention, more leaf area present at harvest due to reduced disease, faster green up after cutting, higher yield, more protein, and 10 points better relative feed value (RFV)

What benefits do you actually observe?

  • Corn: The plant is much healthier in conditions where disease is present.  I also see growth stimulation, even in the absence of disease, slower dry-down (larger window) at harvest, and sometimes higher yields.
  • Alfalfa: For alfalfa, we see some yield benefit in certain situations.  Success appears more limited.  Spraying as soon as you can get into the fields in spring on first cutting has the highest return on investment due to cooler and often wetter conditions. University of Minnesota data demonstrates this.  The healthier lower canopy and leaf retention is real and noticeable, as is quicker regrowth.  Usually, a few fields on a farm could and do benefit from fungicides, but it is not a blanket approach. Generally, spraying fungicide on new seeding is not profitable.

We have done some field trials with growth stimulators and foliar nutrients and are more encouraged by these applications than fungicide.

For corn silage, when should a fungicide be applied?  What about split applications?
Time is critical for the fungicide to work since it is not active beyond 14 days.  We recommend applying at tasseling/pollination since this is the critical time for corn.  Some producers split and/or apply two applications at both V6* and tasseling.  However, we feel there is a more questionable return on splitting applications since the V6 stage does not have the same disease pressure/stress as tasseling.

Under what conditions is spraying a fungicide most beneficial for corn silage?
We use a checklist to determine if fungicide should be used.  Generally, we recommend using fungicide if one or more of these factors apply:

  • Disease-susceptible hybrids
  • Disease present at threshold levels
  • Specialty corns or high value crops (BMR)
  • Corn-on-corn rotations
  • No-till
  • Weather conditions are conducive for disease development
  • Irrigated corn
  • River bottom fields
  • High population fields
  • Fields with high yield potential

Generally speaking, fungicide appears to benefit corn silage since we are protecting the entire plant, thus translating into more yield.  The longer dry down – and extending the harvest window – is an extreme upside for our producers and custom harvesters.

Do you see a special need for applying fungicides next year based on a relatively mild early winter and perhaps less frost under the snow? 

No, our need for fungicides comes with weather at the time of application and due to yield potential of the field.  We always have microbial inoculum present in the air and soil to infect plants with disease, but they only become a real issue if the weather/environmental conditions are conducive for their development.

Do you have any additional comments to share?

The higher the yield, the more response you get from use of a fungicide.  If corn is low-yielding, other issues are probably at play and, correspondingly, the response from the fungicide may be limited.

We see a definite response difference based on genetics as well. Your seed advisor should be able to help define those for you.  A field that has a high yield potential, is planted after corn, and is more susceptible to disease should be sprayed.  I believe BMR corn silage is a strong candidate to spray due to less disease tolerance, reduced standability and its high value per acre.

*V6 is the stage at which the collar of the sixth leaf is visible.  It lasts about three days and occurs about 25 to 32 days after planting.

Category: Crop varieties
Forage Foundations