Fungicides on Corn Silage, By Adam Parker from Maizex Seeds

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The use of foliar fungicides is becoming much more common in corn silage production as these applications have consistently demonstrated yield improvements as well as improved feed quality by means of increased digestibility and reduced toxins.

The past two weeks have been very hot and dry. What does this mean for applying fungicides for this year? Fungicides primarily control fungal leaf disease that are detrimental to the corn crop. For fungal diseases to affect the crop, there needs to be three parts to the disease triangle: the environment, the host, and the pathogen. When considering the hot and dry weather we have been in, generally the risk of disease pressure is low. However, our anecdotal comments would say that fungicides also help improve plant health and help the crop better tolerate stress. Fungicides, and more specifically Strobilurins, have shown to help the crop tolerate drought stress better than untreated areas. This means there could be benefits to application even though the risk of foliar leaf diseases is low.

When evaluating the use of foliar fungicides, you should consider a few things. What is your main goal? Are you trying to maximize your tonnage or are you trying to improve your feed quality? There are different types of fungicides that will target those goals, and you should make sure you choose the right product for your end goal.

Strictly speaking, there are three commercial fungicides that will help to suppress ear moulds. They are Caramba, Proline 480 SC, and Miravis Neo. Other fungicides may reduce leaf diseases and improve yield but will not have any impact on ear mould and mycotoxins. If you would like to target both increased yield and improved quality, you would need to go with a product like Miravis Neo that offers both actions or combine Headline Amp with Caramba to achieve both goals.

In advance of corn flowering, it is difficult to predict the risk of ear mould infections. Even under dry conditions, a sudden switch to rainfall and high humidity can suddenly increase the ear mould risk. The susceptible period for your silage corn to become infected with DON (mycotoxins) is at pollination when the silks are still green. This is usually in a window of 4–6 days after first silk emergence (R1); wet or humid weather at this time can elevate the risk for ear mould infection.  Making sure that you choose the correct fungicide product and hit the target window will be necessary if you want to suppress ear mould and reduce DON toxins in your silage. These products need to be applied when the silks are emerged and before they turn brown. If you are outside of that window, the spray will be ineffective in reducing mycotoxins. Here is a good link for identifying the stages of corn growth:

https://www.agry.purdue.edu/ext/corn/news/timeless/GrainFill.html

Another pest that we have seen over recent years is Western Bean Cutworm (WBC).  This insect pest eats and damages the ear of corn plants and provides an increased risk of DON infection. It is recommended to scout your fields for this pest around tasseling time and spray if you reach threshold. The insecticide timing can be close or overlap fungicide timing and can be more cost effective in justifying the application cost. If WBC is a concern, it is best to target the correct timing for the insecticide and add the fungicide to the tank mix. Insecticides that are commonly used for WBC control are Coragen, Delegate, and Voliam Xpress. For scouting tips on WBC please visit:

http://fieldcropnews.com/wp-content/uploads/2019/07/WBC-Scouting-and-Management-2019-Corn-Final.pdf.

A common question we get regarding applying fungicides and insecticides to corn fields is whether a farmer should hire a ground application through a sprayer or have it done with a helicopter aerially. Both options are effective in applying these products.

From a video demonstrating a sprayer application of VT fungicide on corn.

Where we would focus your attention to detail would be on ensuring the correct product is being applied for your end goal and sufficient water volumes are being applied for ideal coverage (20 gal/ac is recommended for ground application and 5 gal/ac for aerial applications). Be sure to target the correct timing for fungicides and insecticides, as applying outside of the preferred window is not effective. Also, sometimes custom operators or retailers will try to simplify their logistics by running only a few products through their applicators. Be sure to ask for the correct product for you farm based on your needs.