Juggling fungicide variables

Jun 01, 2021

By Darrin Holder

Achieving and maintaining success as a farmer is a challenge, to say the least. 
To be effective, we must stay ahead of the technology learning curve, keep our eyes on the budget, and make sound strategic decisions. Fungicide — whether to use it or not — is a good example of these challenges. 
Unfortunately, there is no “one-size-fits-all” approach that makes financial sense when it comes to spraying fungicides. The successful farmer will weigh a multitude of variables and compare them against current commodity prices before making his or her decision.
But first, it helps to fully understand what response-to-fungicide (RTF) rankings mean. When a new corn hybrid is released to the market, Winfield Technical Seed Agronomists and Answer Plot Crews evaluate them for their RTF. Basically, we spray multiple reps of those hybrids with a fungicide alongside an identical untreated check (set of rows) of the exact same hybrids. 
Then, throughout the year, we conduct disease rankings — pre- and post-application — to get an idea of what the disease pressure is, which fungicide products are working best, and so on. At the conclusion of the season, we take all that information, along with yields, look at it holistically, and then segregate it into low-, medium-, and high-disease pressure.
With the hybrids specifically, we evaluate them across all environments. How does Hybrid A respond to a particular fungicide versus Hybrid B? How does the yield turn out? At that point, we can assign them a designation of low-, moderate-, and high-response to fungicide, or RTF. 
What does RTF mean?
A low-RTF hybrid means that the yield response was right at or below the break-even point when you consider the fungicide and application costs versus the commodity prices for that year.
A moderate-RTF hybrid is right at or above break-even for those same variables. Sometimes you will gain a little, sometimes you’ll be slightly under.
Then, a high-RTF hybrid is always well above the break-even point. They’re no-brainers. Regardless of the disease environment, they will pay. 
What do these yield differences look like? In 2020, we saw a range of anywhere between 3.9 and 35 bushels per acre. This means one of the low-RTF hybrids saw only a 3.9-bushel advantage after being sprayed with a fungicide, while one of the high-RTF hybrids produced a 35-bushel advantage. Both were planted in the exact same environment and were sprayed with the exact same product.
Remember, all of these hybrids are good products that the producer should consider planting based on local performance, soil type, and management practices. When we talk about RTF, we’re only talking about the yield response to being sprayed with fungicide — not the overall yield.
How do I use RTF rankings?
So, how do you, the grower, use this information on your farm? To begin with, you should look at current prices. Just like death and taxes, you can count on the fluidity of commodity prices. Some years, they’re up; some, they’re down. Last year, 2020, was a down year, which meant that a smart grower would have to decide whether or not to invest in fungicides on a hybrid-by-hybrid basis. On an up year, like 2021, those decisions will be different. In both cases, return-on-investment (ROI) is the ultimate determining factor, and you must ask yourself the question, “By spraying this field, will I make money or lose it?” Clearly, we all want to make it, and the way to do that is to use the data that is available to you and make strategic decisions.
Let’s just take the low-RTF hybrids in 2020 when corn was around $3.50 per bushel. At that price, the low-RTF corn — those near that 3.9-bushel number — wouldn’t cover cost. They would have to be closer to nine or ten bushels to break even. But for the high-RTF hybrids, corn would’ve had to been around $1 a bushel for them not to pay.
Okay, so you have the RTF data and you’re looking at the upcoming season. Here is a good approach to take:
The high-price year approach 
($5-6 corn)

High-RTF hybrids: Put those input dollars aside and plan to spray fungicide. 
Get with your local Co-op or GreenPoint Ag location to schedule your application. You have a great opportunity to see a return on your investment.
Moderate-RTF hybrids: You should probably go ahead and put dollars aside and schedule your application for these as well. You still have a good cushion on yield versus price.
Low-RTF hybrids: Consider a wait-and-see approach. What environment do I plant them in? Is it conducive to disease? Am I seeing extended periods of moisture? Is the field no-till or worked ground? Are you planting early or late? Will the field be corn-on-soybeans or corn-on-corn? (If it’s the latter, the inoculum from the previous years’ disease will still be there.) Set dollars aside for a possible treatment, but don’t use them until you know you need them. Don’t schedule treatment yet.
The low-price year approach ($3 corn)
High-RTF hybrids: These will still get a fungicide treatment. Remember, high-RTF hybrids will always get a fungicide treatment unless corn is $1 or below, and I don’t see that happening, so approach these the same as in a high-price year.
Moderate-RTF hybrids: Pump the brakes and see how the season unfolds. Just like low-RTF hybrids in a high-price season, set those dollars aside but see how the year unfolds.
Low-RTF hybrids: Don’t spray. There’s just not enough yield response for these varieties to return your investment in a down year.
In case of southern rust
The exception to these guidelines is the presence of southern rust, a disease caused by the pathogen Puccinia polysora. Southern rust generally develops in the southernmost corn states and then moves north via prevailing winds if the conditions are favorable. (These usually involve high temperatures and humidity.) Although southern rust is fairly uncommon in the Tennessee area, it’s certainly worth planning for as we see it every few years or so. If it appears, I recommend kicking into protection mode. Instead of shooting for incremental bushels based on RTF, you need to do everything possible to protect your available yield, and that means spraying fungicide.
Adjuvant? Yes, please, and thank you
If and when the time comes to spray fungicide, you should do everything you can to make that product pay, and that includes using a high-quality adjuvant. This holds true regardless of which fungicide you’re using, whether you’re using a ground rig, a high-clearance rig, or even a helicopter or airplane. I highly recommend WinField® United MasterLock® for doing a superior job of controlling drift and improving deposition to get that product all the way up and down throughout the canopy.  The last few years, we’ve seen a 3.5- to 5-bushel advantage when adding the MasterLock to the fungicide application.

Remember, as a Co-op member or customer, you have access to a great deal of experience and expertise in the agronomy professionals at your local store. Don’t hesitate to reach out and schedule a fungicide consultation. 

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