I’ll be honest, I didn’t expect to be talking about soybean disease pressure this far north this early in the season. But it’s happening.
From conversations with other farmers and what I’ve been reading lately, fungal disease pressure, especially Cercospora leaf blight, is starting to creep into areas that haven’t had to think much about it before. The mix of early canopy closure, warm nights, and humidity is setting the stage in parts of Minnesota, the Dakotas, and beyond.
Here’s what I’m keeping an eye on:
- Cercospora leaf blight – shows up as a bronzing or purpling on the upper leaves and pods. Easy to miss, but it can cut into yield and seed quality if it sets in early.
- Frogeye leaf spot – traditionally a southern issue, but we’re hearing more reports of it farther north. Watch for small circular lesions with dark margins.
- Sudden Death Syndrome (SDS) – more tied to planting conditions than in-season weather, but if you see yellowing and leaf scorch mid-to-late season, it might be worth testing for.
A few things to note:
- Rotation helps – but a tight corn-soy rotation alone isn’t always enough anymore.
- Fungicide timing matters – R3 (beginning pod) is still the key window for most of these issues.
- Every field is different – some will cruise through clean, others will surprise you.
Additional Resources
- Soybest Disease Risks Rising Across Midwest – article from Agriculture.com
- Overview of Cercospora Leaf Blight of Soybean – CropProtectionNetwork.org
- Frogeye Leaf Spot: The Silent Killer of Soybeans
Let’s Talk Seed Before This Season Ends
If you’re seeing soybean issues in your own fields, or just trying to make sense of what this year’s weather is throwing at us, I’d love to hear about it. We’re keeping a close eye on how hybrids and varieties are responding, and now’s a good time to start thinking through seed plans for next year. Whether it’s corn or soybeans, we’d be glad to help you find something that fits your acres.
Tim Thurmer
Thurmer Seedworks
From our family to your farm.