More agronomists talk about applying fungicides on soybeans than they did five years ago, and for sure 10 years ago. If you already apply fungicides on soybeans, how do you maximize return on investment? If you haven’t applied fungicides before, should you consider doing so in 2024?

Here are answers to key questions like these from three Syngenta agronomists scattered across the Corn Belt: Phil Krieg, covering southern Illinois and southern Indiana; Nick Groth, based in Dodge County in eastern Wisconsin; and Travis Gustafson, in central and western Nebraska. Note that answers sometimes vary based on location and experiences within a local environment.

Why should you apply fungicide on soybeans?

Krieg: Just as with corn — for disease prevention and plant health. In soybeans, strobilurin-resistant frogeye leaf spot has become more common. With earlier planting, septoria leaf spot in the lower canopy is seen quite often. Target spot in the South has also become a risk.

Groth: Miravis Neo and Miravis Top both contain Adepidyn technology, a carboxamide SDHI mode of action that offers great control of key diseases. It has great efficacy on strobilurin-resistant frogeye leaf spot.

Adepidyn also offers superior plant health benefits. Disease in soybeans, like corn, is sporadic and environmentally driven, but plant health benefits that allow the plants to tolerate stress are impactful nearly every year.

Related:Spraying fungicide: Time of day matters

Gustafson: Over the last four years across Nebraska and Kansas, we’ve seen a consistent yield bump around 4 bushels per acre when using Miravis Neo on soybeans. We’re controlling diseases such as frogeye leaf spot and cercospora, but the main benefit is plant health. The crop uses water more efficiently, photosynthesizes more efficiently, uses nutrients better and stays greener longer. All these benefits translate into more yield.

How do you determine timing related to growth stage?

Krieg: The best ROI in soybeans is still R3. You’re setting soybeans up for a healthy R4 stage. At R4 the soybean is still growing, blooming, setting pods and starting to fill grain in lower pods. The risk for pod and blossom abortion is highest. The soybean is working its absolute hardest at R4.

Groth: There has been a consistent message that the best time to apply is during R3, when a pod is 3/16 of an inch long at one of the four uppermost nodes on the main stem with a fully developed leaf. It’s the best time due to rapid yield determination during this period, and the increase in potential disease development. There are times where an earlier application may have benefits, such as if you’re battling white mold. But in most cases, even if there is some risk of white mold, R3 will still be the appropriate timing. 

Related:Long residual sets soybean fungicide apart

Gustafson: If the field has a history of white mold, we will target Miravis Neo toward the end of June, when first flowers come out. White mold infects through flowers, so we need to protect flowers with a fungicide. If the grower is targeting other foliar diseases, we will time the Miravis Neo for R3.

Is overall gallonage in the application important?

Groth: When we make applications for white mold, spray coverage is critical. We need products getting down to the lower flowers to protect against white mold. Increasing spray volume per acre is the best way. For other applications, coverage is still important, but benefits will be less dependent on spray coverage.

Krieg: Application success is more dependent on proper unit calibration and operator skill. Aerial, drone and ground rigs are all effective if carried out properly.

Groth: The better the coverage, the more the plant will be protected. Coverage is especially critical when dealing with white mold.

When it comes to how fungicide is applied, there is much debate. It is hard to beat a ground rig. But I have also seen lots of success with aerial applications from airplanes, helicopters and even drones. When applying aerially, follow the label and apply at least 2 gallons per acre of carrier with Miravis Neo or Miravis Top fungicides. 

Can insecticides be added with the application?

Groth: Insecticide can and often should be added. Fungicides are generally recommended at R3, which often coincides with the heaviest insect pressure in soybeans. Stinkbugs, Japanese beetles and soybean aphids are common pests that occur at that time.

Recently, stinkbug pressure has been on the rise in Wisconsin. These pests are especially frustrating because of direct damage to pods and beans developing inside. Another growing concern are soybean aphids resistant to pyrethroids. It is a growing issue in Minnesota now.

Because of these issues, Syngenta recommends Endigo ZCX, which contains lambda-cyhalothrin, thiamethoxam and Zeon technology. Thiamethoxam has several advantages, including longer residual, translaminar movement from top of leaf to bottom, and effectiveness on pyrethroid-resistant populations. In addition, Zeon helps protect against degradation from rain and UV damage.

Gustafson: Our data from Nebraska and Kansas shows that adding Endigo ZCX with Miravis Neo brings an additional 2 bushels per acre over and above yield gain from Miravis Neo alone.

Krieg: It is imperative that insecticide is added. Don’t just add a typical pyrethroid, because currently we’re trying to control sucking, hard-shelled insects like stinkbugs active in the lower canopy and on undersides of leaves. We must use a systemic insecticide that moves through the leaf and has multiple sites of action. One option is Endigo ZCX — basically Cruiser and Warrior with Zeon technology.

How do you determine if the application was effective?

Krieg: Examine pods and grain at harvest, looking for damaged and aborted seeds and pods. Again, leaving an untreated check is helpful. It all comes down to yield and grain quality.

Groth: One unique thing about Syngenta fungicides that contain Adepidyn technology, such as Miravis Neo or Miravis Top, is that you can see them start to work almost right away. Within five to 10 days, you can often see a visible greening difference between treated areas and the untreated check.

Gustafson: We will see good disease control and soybeans standing tall at harvest. We will also see good pod fill because of plant health benefits.