Do Your Soybeans Need Fungicide Application?

Sally Krueger

Jul 25, 2018

It's a common question – should I spray my beans with a fungicide? The responses swing back and forth between both ends of the spectrum, and trustworthy, respectable agronomic resources have vastly different opinions of how this decision should be made. It’s actually a complex question that seldom has a single answer or one-size-fits-all solution for every farm.

Whether you’re worried about brown spot, cercospora, frogeye leaf spot or something in between—or if you’re not sure what to worry about yet—there are many factors that come into play when deciding if a fungicide application is right for your farm, including:

  • Variety: Varieties with resistance to various fungal diseases, such as white mold or powdery mildew, are widely available. Double check with your seed provider to see how your varieties will stack up against disease pressure.

  • Overall Yield Potential: Before a field even gets planted, you have an idea of what it’s capable of, thanks to yield history, average variety performance, and FBN Seed Finder. A fungicide won’t necessarily increase yield, but it will protect yield if fungal diseases show up.

  • Weather: Hot, humid conditions are a breeding ground for fungi. Along those same lines, if the weather has been too dry or other conditions have already limited plant growth, the application of a fungicide may need some additional number-crunching to make sure it’s best for the operation, which leads you to...

  • Fungicide Cost and Grain Value: While these are two very different considerations, you can’t contemplate one without the other. If the cost of fungicide is too high for you, and you are concerned that the value of the grain may be too low to get a return, you’ll need to take a hard look at your breakevens to see if the bushels saved will pay for the product applied. In the same vein, if the cost of fungicide is low and the value of grain high, it makes sense to utilize a fungicide to get every available bushel out of each acre.

Once you have an idea of whether a fungicide application is going to be right for your soybeans, here are some ideas for what you can do to make sure you’re getting the most out of every application:

Scout Your Fields.

Fungicides can be PREVENTATIVE, such as strobilurins, meaning they’ll do an outstanding job protecting your beans from fungal diseases, and they can be CURATIVE, such as triazoles, meaning they can prevent the spread of disease further in the plant. But, they can’t reverse the damage that happens when you aren’t looking. They also won’t be of much help if what you’re seeing is actually bacterial disease. Know what’s in your field and utilize a fungicide that best combats it.

PRO TIP: Consider adding an insecticide to your fungicide app. Insect feeding creates an entry point for fungal diseases to spread, so if you’ve got bugs, hammer them at the same time by adding an insecticide to your tank mix and keep them from spreading into other fields.

Read Your Labels

Labels carry key information about how to best utilize your fungicide product. Know what adjuvants you need, what companion products work best in the tank, and what is the best timing for your product. Fungi have certain periods during which they are susceptible to fungicides, so hitting in the right window is key.

Know Your Rates

Use the full rate recommended on the label for any fungicide application. Lesser rates can lead to non-uniform control and can encourage fungicide resistance, not only this growing season, but in the surrounding fields in the seasons to come.

Use Multiple Modes of Action

Allow us to beat on this drum. From herbicides to insecticides to fungicides, using multiple modes of action allows you to get to most comprehensive control of pests and protects your farm from resistance issues. Select products with different FRAC group numbers to ensure you are utilizing differing MOAs, or utilize a premix that incorporates 2 or more MOAs. ALWAYS READ AND FOLLOW LABEL INSTRUCTIONS.

One Final Tip

Strobilurin-resistant frogeye leaf spot is now found in more than a dozen states, stretching from the Gulf of Mexico into the Midwest. If you find frogeye on your farm, make sure you’re using dual modes of action, in a single product, such as Quadris Top® SBX or in combination, such as Priaxor® with Tilt®.

Quadris Top® SBX and Tilt® are trademarks of a Syngenta Group Company. Priaxor® is a registered trademark of BASF.

Sally Krueger

Jul 25, 2018