Weather: an all-encompassing force that directly affects profitability but answers to no one. While La Niña was anticipated for 2025, it made a short appearance and exited stage left quickly, leaving a neutral climate in the spotlight.

Long-term weather forecasts, already a difficult feat, are more challenging in a neutral climate because one of the major factors isn’t pushing one way or the other. Historically, soybean yields tend to be below-average during neutral climate patterns.¹ Proactive scouting and fungicide application can help you get ahead of disease when yield may be at risk due to weather.

“Soybeans are really a mixed bag, and diseases depend so highly on what the growing season is doing,” says Meaghan Anderson, field specialist with Iowa State University Extension, recommending scouting early and often. 

“Scouting should always be a pretty consistent thing. Throughout the growing season, though, we know different issues wax and wane. It depends a bit on what time of year it is and what you're looking for specifically, but ideally you should always be out in your fields checking fairly often,” she says.

Anderson warns that these are some of the top culprits to be aware of this season depending on how the weather plays out. 

1. Frogeye leaf spot

Frogeye leaf spot can be identified by the round to angular spots with a dark reddish-purple rim, says Anderson. A gray fluffy growth on the underside of the leaf may also occur.

The disease can cause up to 35% yield loss in certain circumstances.²

“Frogeye leaf spot is probably one of the bigger disease challenges that we can actually manage during the growing season if it's a problem,” she admits.

Albre Brown, technical marketing manager for BASF, adds that you should look into the mid- to upper canopy when scouting, especially on newer leaves. 

Frogeye leaf spot thrives in warm, humid weather with frequent rain. 

2. Septoria brown spot 

Small, irregular, dark brown spots on leaves, which can merge into larger blotches, mean Septoria brown spot has appeared. These spots often start on older leaves in the lower canopy but can progress upwards, Brown says.  

Septoria brown spot thrives in warm, wet weather with longer periods of leaf wetness. 

3. Cercospora leaf blight

Cercospora leaf blight is characterized by bronzed leaves that show up in the late reproductive stages. 

“This bronzing happens because toxins accumulate in the plant cells that react to sunlight,” says Brown. “You will often see these bronzed leaves closest to the sun. The leaves end up falling off if the disease progresses.”

Cercospora leaf blight is caused by the same pathogen responsible for purple seed stain, a disease known to reduce seed quality at harvest.

Average yield loss from Cercospora leaf blight is typically less than 10%, but in cases where the disease develops early, up to 30% losses can occur in areas with high disease pressure.³

Cercospora leaf blight thrives in hot, humid conditions and in fields with a lot of plant debris. 

4. Pod and stem blight

Anderson describes pod and stem blight as black, raised specks that appear in linear rows on mature soybean stems. Pods may also develop these specks, but they may not follow the linear pattern seen on stems. These signs are most prevalent when soybeans are nearing maturity, from R6 (full seed) through R8 (full maturity).

Pod and stem blight generally causes losses of about 20% on average.⁴

Pod and stem blight thrives in warm and humid environments.  

Fungicides are a big player in preventing damage from these disease culprits. Anderson explains that foliar fungicide application typically occurs during the R3 (beginning pod) stage but may occur earlier depending on the targeted disease or other field operations.

“Using a fungicide is like hitting a pause button on disease development. It doesn’t hit stop, but it can pause for maybe 3 to 4 weeks, depending on the product, which could get you close to or all the way to maturity,” Anderson explains. 

Brown adds, “Controlling diseases requires both good scouting and good resistance management, so that means proactive fungicide application and using products with different modes of action.”

Revytek^® fungicide was created with resistance management in mind, says Brown. Because it has three modes of action, Revytek fungicide is one of the most comprehensive fungicides on the market. It contains a unique active ingredient, Revysol^®, the first and only isopropanol azole, which gives it both preventative and curative action.

She says Revytek fungicide protects against both disease challenges and environmental stress, which will be useful during an especially unpredictable year. Its molecular structure provides stronger binding, rainfast performance and excellent efficacy. The unique isopropanol azole molecule has a reinforced isopropanol link, giving it the ability to flex to various conformations and fight a broad spectrum of disease and resistant strains.

Revytek fungicide has been proven to increase yield by 9.5 bushels per acre,⁵ and is the No. 1 grower-recommended soybean fungicide.⁶

A fluctuating climate doesn’t have to cause anxiety with great scouting and a solid fungicide on your side. 

To protect your soybeans and maximize your yield no matter the weather conditions, visit Revytek.com.  

_{¹ Yu, C., Miao, R. & Khanna, M. (2021). Maladaptation of U.S. corn and soybeans to a changing climate. Sci Rep 11, 12351. https://doi.org/10.1038/s41598-021-91192-5} 

_{² Wise K, Bradley C, Sikora E, Mueller D, Chilvers M, Giesler L, et al. Crop Protection Network. Frogeye Leaf Spot. 2016. doi:10.31274/cpn-20190620-013.}

_{³ Missouri Soybean Merchandising Council. “Missouri Soybean Disease Field Guide.” Accessed May 7, 2025. https://mosoy.org/wp-content/uploads/2021/03/59934-21-MO-Disease-Guide.pdf}

_{⁴ Kandel, Y., Phillips, X., Gaska, J., Conley, S., and Mueller, D. (2021)  Effect of Planting Population on Stem Diseases of Soybean in Iowa and Wisconsin. Plant Health Progress Vol. 22, Iss. 2. https://doi.org/10.1094/PHP-07-20-0062-RS} 

_{⁵ 2019-2022 BASF, partially/fully sponsored university and consultant small plot replicated soybean field trials and RevX Fields on-farm demos. All treatments applied within the recommended labeled rate range at R3 timing with NIS 0.25% v/v. Trials conducted nationally across 21 states.}

_{⁶ 2022 Stratus Ag Research. Grower survey. BRAND FOCUS 360 Soybean Fungicides — Midwest. Syndicated research.}

_{Always read and follow label directions. Revytek is a registered trademark of BASF. ©2025 BASF Corporation. All rights reserved.}