Mycotoxin Outlook for 2026 Harvest – Part 1
11 Sep 2026
Animal Nutrition & Health
As was discussed in the last issue, many factors influence the development of fungal diseases, and we generally see regional differences in mycotoxin contamination profiles because different climates support different types of molds and different molds can produce different types of mycotoxins. In addition to weather-related factors, anything that stresses the plant increases the risk for disease and potential mycotoxin production.
Technically, infection can occur at any time during the plant’s lifecycle, but silking is when corn is especially susceptible to ear rot-associated fungal pathogens. According to the United States Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) Crop Progress and Condition Report, silking began roughly late June and extended through mid-August, with the majority of silking occurring in July (Figure 1).1 As such, we will focus initially on weather conditions around the time of silking, but the risk for disease continues through harvest, so we’ll also look at how conditions have progressed since silking and it will be very important to continue to monitor conditions throughout harvest.
Figure 1: Progress excerpt from USDA NASS Crop Progress and Condition: Corn in United States, 2026 Report, September 27, 2026. Silking began mid-to-late June and extended through mid-August, with the majority of silking occurring throughout July.1*
As was already mentioned (and covered in more detail in the September issue of The Digest), anything which stresses the plant increases the risk for fungal disease and mycotoxin contamination. Therefore, monitoring crop condition is also of interest. As you can see in the Good + Excellent Condition excerpt from USDA NASS Crop Progress and Condition: Corn in United States, 2026 Report, September 27, 2026 (Figure 2)1, less corn is rated in good (44%) to excellent (13%) condition this year (= 57% total) vs. the past two years. From a historical perspective, at a similar time point in 2019 (one of the more challenging mycotoxin years in recent history), 57% of the corn was also rated good (46%) to excellent (11%). Looking back on data from the 2019 dsm-firmenich USA corn mycotoxin survey (n = 329 samples)2, Type B Trichothecenes (B-Trich; family including deoxynivalenol (a.k.a. “vomitoxin) and related metabolites) were found most frequently (81% positive) followed by Fumonisins (78% positive). Additionally, the mean concentration of positives for B-Trich was 883 parts per billion (ppb) and the mean concentration of FUM was 3,348 ppb in that survey.
Figure 2: Good + Excellent Condition excerpt from USDA NASS Crop Progress and Condition: Corn in United States, 2026 Report, September 27, 2026.1*
*States represented in the USDA-NASS Crop Progress and Condition Report (these 18 states harvested 93% of the 2025 corn acreage): Colorado - CO, Illinois - IL, Indiana - IN, Iowa - IA, Kansas - KS, Kentucky - KY, Michigan - MI, Minnesota - MN, Missouri - MO, Nebraska - NE, North Carolina - NC, North Dakota - ND, Ohio - OH, Pennsylvania - PA, South Dakota - SD, Tennessee - TN, Texas - TX, Wisconsin - WI
Looking at the temperature data from the National Oceanic and Atmospheric Administration (NOAA), July 2026 was NOAA’s joint-warmest July on record (tied with July 2024) at around 1.47 °C above pre-industrial levels. From June through August (silking period), much of the USA was above or much above average temperature (ranking period 1895-2026) with the region around the “Four Corners” (CO, UT, AZ, NM) and southern Florida experiencing their warmest average temperatures on record (Figure 3).3 The NOAA precipitation data is more variable during this same time period, with some areas being below or much below average while other parts of the country had above or much above average rainfall (Figure 4)3. Within the top 18 corn growing states, WI, MN, and ND were on the drier end of the spectrum while states including IL, IN, OH, and KY received more precipitation than average (Figure 4)3. Hotter climatic conditions especially support the molds which can produce Aflatoxins and Fumonisins.
Figure 3: NOAA National Centers for Environmental Information Divisional Average Temperature Percentiles June-August 2026 (Period 1895-2026).3
Figure 4: NOAA National Centers for Environmental Information Divisional Precipitation Percentiles June-August 2026 (Period 1895-2026).3
An additional report of interest when evaluating climatic conditions is the USDA Corn Areas in Drought map generated using U.S. Drought Monitor data. Near the start of silking, 22% of corn production was within an area experiencing drought (Figure 5).4 During the early weeks of the silking period, the percentage of corn production area experiencing drought decreased down to a low of 19% by mid-July but then began to increase starting at the end of July. The entire month of August hovered between 27% to 29% (Figure 6)4. Following several bouts of heavy rainfall in multiple areas from mid-August until early September, corn production within an area experiencing drought declined back to 21% by the end of September (Figure 7).4
Figure 5: USDA Corn Areas in Drought – U.S. Drought Monitor (June 23, 2026).4
Figure 6: USDA Corn Areas in Drought – U.S. Drought Monitor (August 18, 2026).4
Figure 7: USDA Corn Areas in Drought – U.S. Drought Monitor (September 29, 2026).4
Unfortunately, what happened during silking is only part of the picture. While silking is a prime time for infection with ear rot fungi, diseases can occur and spread at any time during the plant’s lifecycle (even once the grain is harvested and in storage). During grain development, kernels are susceptible to physical damage (insects, wildlife, hail) which provide another route of entry for mold spores. Additionally, infection can occur via the forage portion of the plant (especially relevant for corn silage and other corn-based forage feedstuffs). Although summer days may be hot, cooler nights and foggy mornings which create condensation on the plant can provide the perfect environment for molds to grow. As crops stand in the field later into autumn, the weather tends to deteriorate, resulting in cooler temperatures and further exposure to rainfall, frost, and even potentially snowfall. The risk for Trichothecenes (both Type A and Type B) and Zearalenone increases especially in such conditions – this risk can be realized through further spread of disease or increased concentrations as toxins continue to accumulate while viable mold is present. In addition to climatic conditions, many other factors also influence the occurrence and severity of mycotoxins such as planting / harvest dates, crop rotation practices, tillage practices, hybrid and variety specific characteristics (genetic tolerance to disease, angle of ear on plant, husk tightness, etc.), etc. and this high number of factors contributes to the high variability that is known to exist in mycotoxin contamination.
Preliminary predictions:
Understanding what stressors occurred in your area (or the areas you source grain from) can help indicate what mycotoxin(s) to be on the lookout for and may also provide insights into how frequently new crop feeds should be screened following harvest. However, molds do not read textbooks and many factors influence contamination, most of which are not documented or widely available for review, so it is impossible to truly predict what mycotoxins will be present in every bushel of corn. The best way to understand what mycotoxins are in your feed is to do routine monitoring. We welcome sample submissions as part of our annual mycotoxin survey so if you’d like to evaluate your feed ingredients and assess risk in your operation, please contact your dsm-firmenich representative to learn more about our PROcheck mycotoxin testing service Mycotoxin Analysis. For more detailed predictions for your region, contact your dsm-firmenich representatives for additional insights from our prediction tool.
Disclaimer: Many factors influence mycotoxin contamination, and those factors vary across the country / state / county / field and over time, resulting in an extensive range of potential outcomes. The predictions presented in this article are based on an overview of various influential factors and the educated assessment of one dsm-firmenich employee who enjoys compiling this content. In time, mycotoxin analyses will determine the true 2026 crop contamination profile.
Resources:
Additional valuable resources:
08 October 2026
11 Sep 2026
17 Aug 2026
