Figure 1. Progress excerpt from USDA NASS Crop Progress and Condition: Corn in United States, 2025 Report, September 28, 2025. Silking began late in June and extended through mid-August, with the majority of silking occurring in July.

Figure 2. NOAA National Centers for Environmental Information Divisional Average Temperature Ranks June-August 2025 (Period 1895-2025).² 

Figure 3. NOAA National Centers for Environmental Information Divisional Precipitation Ranks June-August 2025 (Period 1895-2025).² 

Warmer and drier weather persisted through much of September, although some areas had a bout of cooler temperatures and received some rainfall during that time. Despite a brief taste of fall weather, drought conditions expanded or intensified during the month of September as indicated by the Corn Areas in Drought³ (Figure 4 and 5) data from the USDA National Drought Mitigation Center at the University of Nebraska-Lincoln. During September, the corn production in an area experiencing drought climbed from 9% to approximately 26%.³ In some areas, like Ohio which has experienced widespread drought conditions again in 2025, the rainfall may be too little, too late to provide much benefit in terms of yield. However, this brief period of cooler temperatures and moisture could increase the risk for mycotoxins such as deoxynivalenol and zearalenone.

Figure 4. USDA Corn Areas in Drought – U.S. Drought Monitor September 2, 2025.³

Figure 5. USDA Corn Areas in Drought – U.S. Drought Monitor September 23, 2025.³

Dry conditions have facilitated the beginning of harvest in some areas and 18% of corn was harvested as of September 28 USDA Crop Progress and Condition Report.¹ The start of October has witnessed more hot and dry weather in many areas with record temperatures expected the first weekend of the month throughout much of the Upper Midwest and Eastern Great Plains. However, with drought conditions and what may potentially be a result of greater use of fungicides which can prolong plant health, some corn is holding onto moisture and not drying down which is delaying the start of harvest in some situations.  Currently, warm weather and below normal precipitation are predicted in many areas throughout much of October. Conditions can always change, and general predictions do not preclude the potential for scattered rainfall and variable temperatures to occur in localized areas. As fall progresses, it is anticipated that more seasonable weather conditions will eventually arrive. The risk for mycotoxins like deoxynivalenol and zearalenone (and various others) increases as weather conditions turn colder and wetter, especially as crops continue to stand in the field beyond maturity.

Understanding the weather conditions and other stressors which occurred in your area can help give insights as to what mycotoxin(s) to be on the lookout for and how frequently new crop feeds should be screened following harvest. It’s difficult to accurately predict mycotoxins contamination due to the multitude of factors which influence contamination types and concentrations. Considering the variable conditions this growing season and presence of other stressors like foliar diseases (e.g., Southern Rust, Tar Spot, etc.), we anticipate potentially greater mycotoxin pressures in the 2025 corn crop in North America compared with what we have witnessed the past few years. Screening feeds and feedstuffs is the current gold standard to realize mycotoxin contamination and potential exposure. If you would like to submit samples for mycotoxin analysis to better understand risk in your feeds and contribute samples to our annual mycotoxin survey, please contact your dsm-firmenich account manager. We hope to have enough samples analyzed by the November deadline for publication to be able to present an official North America Mycotoxin Survey Update in our next issue.

Disclaimer: Many factors influence mycotoxin contamination patterns, and those factors vary tremendously across the country and over time, resulting in a wide range of potential outcomes. The predictions presented in this article are the culmination of review of such factors and the educated assessment of one dsm-firmenich employee who enjoys compiling this content. Time and mycotoxin analyses will reveal what the 2025 crop contamination profile looks like.