This year's corn season has raised new alarms across the Midwest, as ear rot pathogens that once appeared sporadically in the eastern Corn Belt are now showing up more frequently across western cornfields. These molds-Fusarium, Penicillium, and Cladosporium-are not only affecting yields but are also increasing the likelihood of mycotoxin contamination in harvested grain. The implications are significant for livestock feed safety, grain marketability, and the economic bottom line of producers.

According to Purdue Extension corn specialist Dan Quinn, surveys and research are underway to quantify the extent of ear rot outbreaks and to assess their impact. In one striking case, assistant agronomist Betsy Bower visited a June-planted cornfield that had not been treated with fungicides. Even by early September, she found multiple foliar diseases along with at least three active ear rots. These findings are not isolated. Reports of mold activity tied to late planting, high humidity, and insect damage are becoming more widespread.

The affected ears were sent to the Purdue Plant and Pest Diagnostic Laboratory, where John Bonkowski confirmed the presence of Fusarium ear rot, Cladosporium, and Penicillium. Analysis showed that these molds often colonized kernels with pre-existing injury, frequently caused by insects. Some ears contained desiccated caterpillars embedded in moldy kernels. The lab noted that the blackened kernels were particularly associated with Cladosporium growth, while grayish mold near the ear tip was linked to Penicillium.

Understanding which fungal species are present is critical, because not all ear molds produce mycotoxins. Fusarium, for example, is known to produce fumonisins, which are especially toxic to swine and horses. Penicillium species may generate ochratoxins, which can pose risks if conditions are right. By contrast, Cladosporium is generally considered less dangerous from a mycotoxin standpoint, although it can still reduce grain quality and lead to dockage at delivery points. The presence or absence of mycotoxins cannot be judged by sight alone-lab testing is the only reliable method.

The consequences of ignoring this issue are increasingly real. Grain elevators may begin to test more shipments for mycotoxins, and failure to meet safety thresholds can result in price penalties, rejected loads, or the need for on-farm grain segregation. For livestock operations, feeding contaminated grain can lead to animal health issues, productivity losses, and even regulatory violations.

What can producers do as they prepare for 2026? First, scouting for ear rot symptoms late in the season-especially during the dent and early maturity stages-is essential. Second, submitting suspect ears to a diagnostic lab can confirm which molds are present and help guide hybrid selection decisions. As Bower notes, hybrids differ widely in their resistance or susceptibility to these pathogens, and seed companies are now including more disease-resistance data in their tech sheets. Third, adjusting fungicide timing may offer some protection, particularly when applications are made at or before tasseling, the stage when infections often begin. Research from Ohio State University reinforces the importance of early fungicide applications to control ear mold infections and limit mycotoxin formation.

Harvest management also plays a role. Fields with known ear rot pressure should be harvested early, and grain should be dried quickly to below 13% moisture. In high-risk cases, segregating affected grain and cleaning bins to avoid cross-contamination are prudent steps. Moreover, post-harvest sampling and storage monitoring will be crucial in identifying any hidden mycotoxin issues before grain enters the feed or export supply chain.

As more fields across the Midwest experience ear mold infestations, it's clear that the problem is no longer regional-it's becoming systemic. Climate variability, delayed planting windows, and shifts in insect pressure are all contributing factors. By embracing diagnostics, adopting more resistant hybrids, and refining management practices, U.S. corn producers can stay ahead of this growing threat.