Agronomy Blog

Fungicide Applications Corn - Factors to Consider

by Dan Mitchell | Jun 8, 2018

The used of fungicides to protect corn from disease pathogens has gained wide acceptance in the last several years. This is due to a combination of factors like improved fungicide options, heavy disease pressure and a fairly reliable response of today’s hybrids to the treatments. The one “wild card” in all of this however is the price of corn at the elevator.

While fungicide applications do in most cases improve health they may not always produce an economic return on yield. With corn hovering around $4.00 a bushel the return on investment for fungicide applications gets to be more critical. For this discussion I have narrowed it down to three topics, economics, expected hybrid response and disease pressure.

Here are some scenarios showing the economics of fungicide applications. For simplicity this chart only refers to single applications generally made at VT-R1.

The disease tolerance of your hybrids and response to fungicides can be found in LG Product Guide or by contacting your local representative. LG Seeds evaluates our hybrids for the likelihood of a positive response in yield to fungicide applications. A key factor in assigning a response score is a combination of yield potential of the base genetics and the overall “disease package” of that hybrid. Put simply, a hybrid with very high yield potential that may have an average disease package will generally be scored as “High Response” and will have a numeric score of 8 or 9. On the other hand a hybrid with good yield potential but has a very good disease package will probably be moderate response and carry a numeric score of 7 or less.

Disease pressure will vary widely from region to region and year to year. Growers in the upper Midwest tend to be more concerned about Northern Corn Leaf Blight, Anthracnose Leaf Blight and Gray Leaf Spot while growers in the Mid South are probably looking at Southern and Common Rust along with Gray Leaf Spot s their two biggest concerns.  Most university experts agree that timely scouting and applying “as necessary” is still the best economic approach. Preemptive sprays at VT-R1 however have become quite common in the mid-south due to the high likelihood of Southern Rust moving up from the gulf states in July and August. Many of these growers saw losses of 20 to 40 bushels per acre in 2015 and 2016 and have thus adopted planned applications of fungicides.

Whichever approach you take, the idea is to keep the upper portions of the corn plants as free from disease as possible. The need for leaf health above the ear is crucial to finishing out the ears to their maximum potential.
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In conclusion, keeping a close watch on your crop and paying attention to nearby university reports are two good ways to be prepared to make spraying decisions. The final piece of the puzzle comes down to which product do you apply and when. Consult your local ag chem retailer for the best product(s) for your area. The chart below shows most of the options available for use in 2018.

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Resources and Additional Information

  1. Fungicide Efficacy for Control of Corn Diseases. Dr. Kiersten Wise Purdue Botany & Plant Pathology Jan2017
  2. News.UTcrops .com - Foliar Diseases and Fungicide Applications in corn.2017/06

Note: The information in this issue is based upon field observations and third-party information. Since variations in local conditions may affect the information and suggestions contained in this issue, LG Seeds disclaims legal responsibility therefore. Always read and follow label instructions.
LG Seeds and design are trademarks of SCA Limagrain.

Download a copy of this Technical Bulletin: Tech_381 - Fungicide Applications in Corn