Beckman shares concerns about conditions appearing in corn fields

Today I want to share some timely insights from Dr. Shelby Gruss, Assistant Professor and Forage Extension Specialist with Iowa State University. She recently wrote in Iowa State’s Integrated Crop Management News about some unusual conditions showing up in corn fields this summer that could affect silage quality.

This summer has been both hot and wet, with consistent rainfall across much of the region. These conditions have led to wrapped tassels and southern rust—both raising questions for silage harvest.

Wrapped tassels aren’t something we often see in the Midwest, but this year it’s been widespread. Wrapped tassels happen when tassels emerge before the flag leaf has fully unfurled.

For silage, the big concern is pollination. Since starch content comes from the ear, poor pollination can mean lower starch levels in the harvested forage. While overall yield and other nutrients aren’t expected to be hit as hard, research is limited because this problem is so rare.

Southern rust, on the other hand, may pose a greater risk. Since appearing in July, it has spread quickly in warm, wet weather. While southern rust itself doesn’t produce toxins, it weakens plants and opens the door for stalk rots like Fusarium and Gibberella, which can produce harmful mycotoxins.

Another possible result of this fungus is a rapid dry down. Crops in the region have started turning and progressed quickly. Southern rust pustules rupture the epidermal tissue, making it difficult for the plant to regulate water—so as conditions change and plants begin to mature, it makes sense why dry down has been so swift.

Catching a quickly drying crop at the right stage for harvest is important. When it comes to harvest decisions, timing and moisture are still key. Monitor fields closely as we approach harvest for disease progression and plant health. Conditions may change more quickly than we are used to. And don’t wait too long if standability is becoming an issue. Harvesting at the right moisture not only helps with packing and fermentation, but also minimizes losses from lodging or further disease development.

For silage, southern rust brings three main concerns: • Early dry down, which can hurt fermentation.

• Reduced yield and starch content if grain fill is limited.

• Lower nutritive value, with research showing up to a 13% decline in digestibility.

Finally, this summer’s wet conditions are also favorable for ear rots like Gibberella, Fusarium, and Diplodia—many of which can produce mycotoxins that impact livestock health.

If you’re concerned about silage safety or quality, testing is a smart step. While not all offer it, many university diagnostic labs and commercial feed testing services, offer mycotoxin screening and forage analysis to help ensure feed safety. These tests can be a bit pricey, so some preliminary field scouting to confirm a risk may help ensure they are money well spent.

This information was adapted from an article originally published August 20, 2025, by Dr. Shelby Gruss in Integrated Crop Management News from Iowa State University Extension and Outreach.

Putting up quality silage always takes careful management and timing, but mother nature has thrown a few extra hurdles in the way to keep us on our toes for the 2025 harvest season..

Ben Beckman is a beef systems Extension Educator serving northeast Nebraska. He is based in the Cedar County Extension office. You can reach him at: (402) 254-6821 or email: [email protected].