For years, crown rot was viewed through a narrow lens—a single pathogen causing a single problem. But researchers at the University of Nebraska and Iowa State University suggest the reality is much rowdier. They report that crown rot often behaves like a disease complex rather than a solo act.
According to Alison Robertson, Iowa State University Extension field crops pathologist, the disease is frequently the result of a “party” of organisms. Robertson and Tamara Jackson-Ziems, University of Nebraska field crops pathologist, have often found a crowd of fungi – including Fusarium graminearum, the organism Phytopythium ambiguum (nicknamed “Pam”) and others – within the same rotted crown.
“One of the big unanswered questions is which ones start the infection, which ones join later, and which ones are just saprophytes feeding on dead tissue,” Robertson says.
Jackson-Ziems adds that she and Robertson are exploring the possibility that these pathogens must work together to produce the severe symptoms growers frequently see in their fields. While this complexity makes the disease harder to address, the researchers offer five practical steps you can take to prevent or minimize the impact of crown rot this season..
1. Evaluate Corn Hybrid Disease Ratings
While few if any hybrids are currently scored specifically for crown rot, field work in Nebraska shows clear differences in how various genetics handle the disease. Jackson-Ziems advises looking beyond general disease ratings.
“Talk with your seed dealer about data on hybrids specific to crown rot or early plant health,” she suggests.
Matt Essick, Pioneer agronomy innovation leader, notes that other traits are your best defense. Trait scores such as stress tolerance, stalk strength and stay-green can help combat symptoms, he explains.
2. Manage Early-Season Stress
Crown rot is heavily linked to “wet feet” and cold starts. While it is difficult to replicate the disease in a lab, Robertson notes practical experience shows that planting into cold, saturated soils—especially in fields with a history of the disease—is an invitation for trouble.
Brett Leahr, a regional agronomist with AgriGold, points out that poorly drained areas and compacted soils are particularly vulnerable.
He says a lack of strong freeze and thaw cycles to break up Midwest soils in recent years has allowed compaction layers to build, trapping moisture and stressing young roots.
Fertility also plays a defensive role. “Tissue sampling can show farmers where their nitrogen is, especially at an early stage,” Leahr reports in a press release. “Making sure nitrogen is adequate ... is key to minimizing risk.”
3. Set Realistic Expectations for Fungicides
While lab tests show that “Pam” and various Fusarium isolates are sensitive to common seed treatments and in-furrow fungicides, field results have been less consistent.
“Field trials in Iowa so far have not consistently produced crown rot to prove a clear yield or disease benefit,” Robertson notes.
Pioneer’s Essick agrees that while these products may suppress early infections, they aren’t a silver bullet. The most effective strategy remains maintaining overall plant health by reducing environmental stress and preventing insect damage to the roots.
4. Scout Early And Bring A Shovel
Farmers frequently notice crown rot at around dent stage (R5), but Robertson and Jackson-Ziems say the damage often starts earlier, between V3 and V6. They tell farmers to keep an eye out for stunted, pale or off-color plants in the midst of healthy plants.
“The first thing we might notice is that some plants may die early, and leading up to that, you might see some really odd discoloration. We call it ghosting—an off, ugly, greenish-gray color where the tops of the plant die,” Jackson-Ziems explains.
To confirm your suspicions, dig up the dead plant, wash the roots, and split the crown lengthwise. Look for brown, discolored tissue and root loss.
If you find significant “ghosting” in fields, Leahr recommends a proactive harvest strategy. “If you see a lot of ghosted plants in the field, consider making plans to harvest it early,” he says, suggesting a 5% threshold for prioritizing those fields.
5. Document And Share Your Findings
Because so much is still unknown about crown rot, on-farm data from affected fields is invaluable. Robertson and Jackson-Ziems encourage growers to keep detailed records of planting dates, soil conditions and hybrid performance.
Also, consider diagnostic testing of affected plants and sharing the results with your agronomist and university Extension specialists. What you share can contribute to a larger pool of knowledge about the disease. The faster researchers can identify which organisms are leading the “party” in your corn crop, the faster they can develop the tools needed to help you shut it down, say Robertson and Jackson-Ziems.
Learn more through the Crop Protection Network’s Frequently asked Questions about Crown Rot in Corn. Robertson and Jackson-Ziems also offer more insights in their presentation on the topic, available here.
