Blog Archives
Harvest Grain Quality Concerns 2026
I’ve been thinking of the grain quality concerns and safety with the upcoming harvest. We all know how crazy it’s soon to get with harvest. Unfortunately, most of the corn and soybean are ready now at the same time. It’s hard to know how to prioritize harvest. Normally, we’d go by percent stalk rot in a field of corn and percent moisture in both corn and soybean. Perhaps there’s still ways to prioritize based on those factors, but now we have the additional concern of looking at grain quality as well in both crops. The following article has tips as one faces harvest these coming weeks: https://cropwatch.unl.edu/harvest-2025-prep-guide-minimize-losses-disease-stressed-corn/.
For stalk rot assessments: Push at least 100 corn plants to arm’s length about 30 degrees from vertical. If plants bend below the ear and don’t snap back upright, they have a greater chance of lodging at or prior to harvest if there’s high wind events or heavy rain. I prefer the pinch test in which one squeezes the lower internodes to assess stalk strength and check for stalks that are easily crushed by hand.
Both corn and soybean have sprouting occurring in the field. In corn, this is particularly occurring where ears are upright with tight husks. With soybean, it’s occurring where the beans in the pods dried down to 13% or less and rewetted to at least 50% of their seed weight with the rains. There’s also a number of fungal kernel rots occurring in corn. Fusarium and giberella have a white/pink/red fungal growth. The presence of the fungus doesn’t guarantee mycotoxins are present, but potential mycotoxins that can be associated with these fungi are vomitoxin and fumonisin. White fungal growth that overtakes an ear and makes it feel very light is diplodia. There are no mycotoxins associated with it. There’s also a number of “lesser fungi” that cause cob rots that we’re also seeing this season.
It’s important to know what’s impacting the corn ears prior to harvest, binning corn, or taking it to the elevator. If a particular hybrid is more impacted by kernel rot than another, make sure not to put that corn in the same bin as corn with better quality. Grain affected by ear rot diseases and mold are less suitable for storage. Use or sell affected grain first and store the highest quality corn possible. Grain needs to be cooled to 55F and at 13-14% moisture in order to stop Fusarium and other fungi from continuing to grow in the bin. More info. at this resource: https://cropprotectionnetwork.org/publications/storing-mycotoxin-affected-grain
For soybeans, it’s also important to know if the variety in the field is impacted by things like purple seed stain or Phomopsis seed decay, which can cause elevators to reject soybeans. If you’re noticing discolored soybeans, talk to the elevator beforehand. Both of these conditions are variety related so keep track of which varieties you observe these conditions in.
Set combine fans to blow out as many broken/damaged kernels from insects, fungi, or sprouting as possible. Adjust combine settings to reduce harvest losses due to brittle kernels. Aim to start harvesting fields at a higher moisture (above 17%).
It will be a dirty harvest as secondary fungi can turn the leaves and stalks a blackish color. Fungal spores may behave like dust and aggravate respiratory illness or symptoms in sensitive individuals. Consider wearing dust masks or respirators when working in affected fields or around grain, such as in grain bins. Check air filters on equipment operating in conditions with a lot of dust and spores. Keep fire extinguishers close at hand. Take breaks as needed — and care for your mental, emotional and physical well-being. Be careful on roads: use headlights especially on gravel roads and check intersections before proceeding through them in the country. The Nebraska Rural Response Hotline is 800-464-0258 and is available for emotional support, legal and financial assistance, and disaster relief. Wishing everyone a safe harvest and hoping yields aren’t impacted too much from the challenges.
Corn Observations
Grain Storage
There’s over 25 species of fungi that can produce ear molds with the majority of them ceasing growth at 14% moisture within the kernel. For short term storage of moldy grain, drying to 15% moisture as quickly as possible can greatly slow additional fungal growth within the grain bin. The table below shares the days required to dry corn to 15% moisture with 1.0 cfm/bu and various temperature and humidity conditions. More info. at this resource: https://cropprotectionnetwork.org/publications/storing-mycotoxin-affected-grain
“Since drying time is directly proportional to the airflow, the producer can calculate the estimated drying times when using airflows other than 1.0 cubic foot of air per minute per bushel (cfm/bu). For example: Table II shows when drying corn from 18 percent to 15 percent moisture with 50F and 50% relative humidity air, the estimated drying time is 12.5 days using a 1.0 cfm/bu airflow. If the airflow is 1.25 cfm/bu, the estimated drying time would be 12.5 days / 1.25 = 10 days. For 1.5 cfm/bu, the drying time would be 12.5 days / 1.5 = 8.3 days. For 0.8 cfm/bu, the drying time would be 12.5 days / 0.8 = 15.6 days.” Source: Management of in-bin natural air grain drying systems to minimize energy cost.
- Management of in-bin natural air grain drying systems to minimize energy cost
- UNL CropWatch Grain Storage Resources
- Managing large grain bins for potential mycotoxin contamination
Mycotoxin Information
In 2026, we’re primarily seeing Fusarium and Gibberella species which have the potential to produce mycotoxins. Thus, the information below is directed at those fungal species and mycotoxin levels that can be associated with them. Again, the presence of fungi does not automatically mean a mycotoxin is present.
The following toxins can be produced from species of Fusarium and Gibberella. Source: Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health, Iowa State publication, 1997.
Source: Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health, Iowa State publication, 1997.
JenREES 1-26-20
Corn Quality Concerns: The two main questions I’ve received: “Are you hearing others mentioning low/variable test weights on corn?” and “Are you hearing of loads being rejected (to ethanol plants) due to mycotoxins?” While I’m unsure how widespread this is, I have been receiving these questions. A reminder to check your grain quality if you haven’t already been hauling or checking it.
Test Weight is a volumetric measurement (weight of corn grain per unit of volume), and as such, doesn’t directly correlate with yield. Standard corn test weight is 56 lbs/bu (1 bushel is 1.24 cubic feet). The size, shape, slipperiness of surface, and density of the kernel impacts test weight. Hybrids can show differences in test weight. Test weight is different than kernel weight, and thus not directly correlated with yield. Test weight gets at how tightly packed the starch is within the kernel. Reducing kernel moisture can allow for increased test weight if the starch loses water allowing for it to be packed more tightly within that kernel. Dry kernels that slide past each other may pack better allowing for increased test weight.
Lower test weights can result with disease, insect, and environmental stresses that impact photosynthesis and the movement of nutrients to the kernel during grain fill. These can include foliar and stalk diseases, drought stress, lack of nutrients, freeze prior to physiological maturity, late planting, and below normal temps during grain fill. Rewetting of kernels in the ear can impact test weight as kernels can swell and not shrink back to the same shape as previously. We know that moisture events happened after physiological maturity causing some sprouting of kernels in some ears prior to harvest. We did have high foliar disease pressure this year and reduced stalk quality. Compromised integrity of the kernel due to insect, disease, and mechanical damage can also impact test weight. I didn’t see the amount of kernel damage as I did in 2018. But there are certain hybrids that are high yielding and widely planted that I tend to see starburst patterns on kernels (due to Fusarium) and shortened husks exposing ear tips to more insect damage/ear molds. There are also hybrids that had a large amount of top dieback, husk tissue that turned brown early, or refuge in a bag plants that died early in fields. All of these may be factors potentially impacting test weight as well. Thinking about photosynthesis, we had reduced solar radiation during grain fill. I can’t help but think that could also impact it but didn’t easily find research that correlates solar radiation to test weight. There’s research correlating solar radiation to yield and kernel weight, though.
Regarding vomitoxin levels, the starburst patterns on kernels, insect damage leading to
ear molds, wet corn not properly dried or cooled in bins can all impact greater Fusarium growth and the potential for vomitoxin to be produced. If vomitoxin (also called DON) is an issue, concentrations can triple in the ethanol process of producing the distiller’s grains. Hogs and poultry are more sensitive than cattle, so the end user may be a factor in addition to the vomitoxin levels. I don’t know the levels being rejected so I can’t speak more to this.
York County Corn Grower Tour: Corn growers and spouses are welcome to join us February 3 for a tour of ag industries in the Lincoln area. We will meet at the York Co. Extension Office at 7 a.m. and will carpool leaving at 7:15. Our first stop will be RealmFive which focuses on wireless connectivity for ag operations. We will then tour Smart Chicken in Waverly which offers retail- and foodservice-packaged organic chickens and antibiotic-free chickens from Kansas, Iowa and Nebraska. Lunch at Lazlos is next followed by learning about the UNL hops program and research using corn gluten meal and soybean meal. Possibly another stop on way home. Please RSVP to me at jrees2@unl.edu if you’re interested in attending by Feb. 2nd. Hope to have a good group who can join us! Flyer at jenreesources.com.
What do Mycotoxin Levels Mean?
Last week I was receiving text messages from a few of our farmers about corn harvest results from damaged corn. Low levels of mycotoxins are being detected in samples thus far, thankfully.
A reminder, the presence of mold does not automatically mean a mycotoxin is present. The fungi producing mold have the potential to produce mycotoxins.
Here’s What the Numbers Mean…
For aflatoxin, the U.S. Food and Drug Administration has set a recommended limit of 20ppb (parts per billion) for dairy animals, 100 ppb for breeding animals, and 300 ppb for finishing animals. To put this is simpler terms, a sample would need 20 affected kernels out of a billion kernels to be at the legal limit for dairy animals. So far, most samples are coming up at 5-6ppb which is very low.
For fumonisin, 20ppm (parts per million) is the recommended limit set by FDA for swine, 30ppm for breeding animals, 60ppm for livestock for slaughter, and 100ppm for poultry for slaughter. So, this would mean 20 affected kernels in a million kernels could cause a problem for swine. Again, our levels are averaging closer to 5ppm right now which are low.
Deoxynivalenol (DON) also known as vomitoxin is another mycotoxin being tested from grain samples. This mycotoxin causes reduced weight gain and suppresses animal feeding, especially in swine. Concentrations greater than 10ppm can result in livestock vomiting and totally refusing feed. FDA has recommended that total feed levels of DON not exceed 5 ppm for cattle and chicken, and 1 ppm for swine.
It is very important to sample from several places in the grain to get an accurate sample for damage and mycotoxins. It is also very important that black light tests are not used to determine the presence or absence of mycotoxins. Some of these mold fungi produce a compound that fluoresces under black light, but research has shown that this quality does not consistently predict the presence of mycotoxins (often provides false positives). Finally, before any of your storm-damaged corn is put in a bin, call your insurance agent out to get a sample!
Protecting Your Health with a Mask
There is some great information from the University of Nebraska Med Center on what types of masks to use to protect your health from molds and potential mycotoxins. Some people tend to have more sensitive immune and respiratory systems than others, so I’d highly recommend checking out these short videos.
Feeding Storm Damaged Corn; a Few Thoughts from a Veterinarian
With the recent sprouting of grain on the ears and with more producers now learning what percent loss their crop insurance is determining for each field, I felt it would be good to talk about feeding this damaged grain again. This post is written by Dr. Dee Griffin, DVM at UNL’s Great Plains Veterinary Education Center at Clay Center. I appreciate Dee’s willingness to provide this information from a Veterinarian’s perspective. 
Also a note, to date we have not found Aspergillus in our hail damaged fields. The grain molds we are seeing are Diplodia and Fusarium. Diplodia does not have the potential to produce mycotoxins. Fusarium has the potential of producing fumonisin, vomitoxin, or DON. You can bring forage samples to Husker Harvest Days this coming week to the IANR building and have them tested that day for nitrates for free if you wish.
Dr. Griffin writes: Any time a growing grain producing plant is damaged there is a potential for changes in the plant or grain on the plant contaminated with fungus/molds to grow. The most common change in stressed plants is the accumulation of nitrates. Aspergillus or Fusarium will be the most likely fungi to be contaminating harvested grain from storm damaged corn in our area.
It is really important to know that most molds are not toxic. Therefore just because mold growth is observed doesn’t mean the feedstuff will harm livestock. Even though a mold may not be toxic it can still cause feed refusal. Not all livestock species are equally sensitive to mold contamination and not all production groups are equally sensitive. For instance pregnant and young animals are more sensitive than mature non-pregnant animals.
Nitrate accumulation in stressed plants can cause be harmless or cause serious harm depending on:
- the level of nitrate in the feed harvested from stressed plants,
- on the life stage of the animal,
- and on the species of animal.
Nitrates accumulate in the forage portion of the plant, so nitrates are not a concern in grain harvested from stressed plants. Additionally, it is important to know nitrate levels will always be highest in the bottom part of the plant and lowest in the top foliage. Nitrate testing is simple and reasonable quick. Your local UNL Extension Educator can help you locate the nearest facility that does forage nitrate testing.
Feed containing nitrate levels less than (<) 1000 parts per million (ppm) seldom are associated with an animal health concern. Feed containing nitrate levels greater than (>) 1000 ppm may be a concern in younger animals and levels >2000 ppm should not be fed to pregnant cattle. Feeder cattle are reasonably resistant to nitrates but feeds containing >4000 ppm should not be fed to any animals.
Molds in corn grain of concern could be either Aspergillus or Fusarium. Your UNL Extension Educator can be a great help in identifying mold growing on ears of your storm damaged corn before the grain is harvested. Both of these fungi are potentially dangerous when found in livestock feed. Toxins produced by molds are extremely stable, therefore if a significant level is found, the level will not decrease over time. Silage produced from damaged plants and grain harvested from mold infested plants is potentially a problem.
Good silage management is critical to lessen the likely hood of continued mold growth after ensiling. Proper packing to remove oxygen and improve fermentation which ensures the pH will be below 4.5 is critical.
You can’t look at harvested grains from storm damaged fields and visually identify mycotoxins. Corn grain from storm damaged fields can … and mostly likely should … be tested for mycotoxins before feeding to livestock. Your local UNL Extension Educator, nutritionist or veterinarian can help with mycotoxin testing.
Proper sampling is crucial to getting reliable results back from the laboratory. A “grab sample” is not adequate. The sample submitted to the lab should be representative of the entire load, bin, pit or pile of feedstuff being evaluated.
The steps are simple
- If sampling a field before harvest, sample at least two dozen ears that appear to have mold growth and submit all the ears to the laboratory for mycotoxin evaluation
- If sampling after harvest, take multiple samples uniformly from throughout the silage or grain in question
- The sample should be taken from what would be used in a single load of feed
- That means, if five loads of feed could be made from a 50,000 lb semi-load of corn, collect not less than five samples from the semi-load of corn
- The sample should be based on sample volume not weight
- For instance, collect “coffee can” size samples
- Mix all the all samples together that were collected from the feed in question
- For instance, if 10 coffee can size samples were collected from across the face of a silage pit, pour all 10 samples onto a plastic sheet and thoroughly mix them together
- Next, collect a single sample from within the 10 mixed samples
- Submit the single sample to the laboratory
The laboratory results usually will provide some recommendations for how the feedstuff can be used. There is an old saying, “Dilution is the solution …” meaning in this consideration, that many feedstuffs that contain higher levels of mycotoxin than would be acceptable, might be usable if a sufficient amount of non-mycotoxin contaminated feedstuff is used to dilute the mycotoxin. Your UNL Extension Educator, nutritionist or veterinarian can help evaluate the possible uses of a damaged feedstuff containing unacceptable levels of a mycotoxin.
Aflatoxin Concerns in #Corn
This article originally appeared in http://cropwatch.unl.edu written by Dr. Tamra Jackson-Ziems, UNL Extension Plant Pathologist.
Drought and high temperatures promote development of the disease Aspergillus ear rot (pictured right). The fungi that cause this disease (most commonly, Aspergillus flavus) can produce aflatoxin. Aflatoxin is one of many chemicals in a group known as mycotoxins that are produced by fungi (molds). Mycotoxins, such as aflatoxin, can be toxic to animal and human consumers and, at certain concentrations, can lead to dockage or rejection of grain at elevators.The unusually high temperatures and drought this summer are having severe impacts on Nebraska corn. In addition to reductions in test weight and overall yield, secondary problems are developing in some corn fields as a result of these conditions.
Corn harvested for grain to this point has been predominantly from fields that sustained substantial drought damage leading to early maturation and plant death. Notable aflatoxin contamination appears to be in a small percentage of southeast Nebraska fields, based on samples submitted to several laboratories in the area.
Mycotoxins are common and can be safely consumed at low concentrations. The concentration of aflatoxin that is considered safe for consumption depends on the age and species of the consumer. An abbreviated summary listing the Action Levels identified by the FDA for aflatoxin is listed in Table below.
Testing for Aflatoxin: Farmers and crop consultants can scout high risk fields for Aspergillus ear rot as an indicator for aflatoxin, but only lab testing of grain samples can accurately identify the concentrations of aflatoxin in the grain. Accurate lab test results for aflatoxin will depend greatly on the quality of the sample that is collected and the laboratory methods used to test it. The test results are only applicable to the sample that is submitted, so it is very important to collect an adequate sample for the best results. Refer to the publication, Sampling and Analyzing Feed for Fungal (Mold) Toxins (Mycotoxins) for recommendations on how to collect and submit a high quality sample for mycotoxin analysis.
Contact and submit samples to a laboratory that is certified by the federal Grain Inspection Service and Grain Inspection, Packers, and Stockyards Administration (GIPSA) for mycotoxin analysis for the most accurate results. A GIPSA website lists laboratories certified to conduct testing in Nebraska. They include
- Lincoln Inspection Service, Inc.;
- Fremont Grain Inspection Department, Inc.;
- Omaha Grain Inspection Service, Inc; and the
- Sioux City Inspection and Weighing service Company.
Some grain elevators and individuals may be using a black light (ultraviolet light) to detect for fluorescence as a method for rapid screening of grain samples. This practice is NOT recommended when making decisions about aflatoxin contamination in loads of grain. The component that produces fluorescence under black light is called kojic acid. Although kojic acid is produced by the same fungus that produces aflatoxin, its presence is not necessarily an indicator of aflatoxin and might lead to false positive results and unnecessary rejection of grain.
High Risk Factors for Aflatoxin Contamination in Corn
- Drought-damaged fields, including rainfed (dryland) fields and non-irrigated pivot corners
- Fields or areas with higher incidence of corn ear-feeding insects, such as the corn ear worm
- Grain damaged before or during harvest or after harvest while in storage
Ear rot diseases and aflatoxin are not evenly distributed across fields or in the grain, so scouting and/or sampling should include a substantial portion, at least several acres. The presence of the fungus in kernels does not always correlate well with the presence of aflatoxin, nor does the absence of visible fungal growth necessarily indicate the absence of aflatoxin.Scouting For Aspergillus Ear Rot
- Open husks to view a large number of ears.
- Look for the presence of dusty yellow-green to olive-green spores, especially on the surface of damaged kernels or ear tips (Figure above).
- Pay special attention to higher risk areas.
Harvest and Storage: If fields have documented Aspergillus ear rot and/or risk of aflatoxin contamination, it is recommended that you harvest and keep grain separate from other grain at less risk, such as irrigated fields. Storage of affected grain is not recommended because ear rot diseases and mycotoxins can continue to accumulate during storage. If storage is necessary, cooling and drying grain to less than 15% moisture within 48 hours of harvest will help to slow fungal growth and aflatoxin production. Grain intended to be stored for longer periods of time should be dried to less than 13% moisture.
Presently, it is too early in the harvest to know the extent of aflatoxin contamination in this year’s corn crop, but at this time only a small percentage appears to be affected.
Resources: For more information, refer to the list of publications below or view this week’s episode of Market Journal.
- Plant Disease Profiles #3: Ear Rot Diseases and Grain Molds, EC1901
- Understanding Fungal (Mold) Toxins (Mycotoxins), G1513
- Sampling and Analyzing Feed for Fungal (Mold) Toxins (Mycotoxins), G1515
- Use of Feed Contaminated with Fungal (Mold) Toxins (Mycotoxins), G1514
- Aspergillus Ear Rot and Aflatoxin Production, Iowa State University Integrated Crop Management News
- Check Cornfields for Aspergillus Ear Rot, University of Illinois the Bulletin
| Table 1: FDA action levels for aflatoxin contamination in corn intended for livestock. | |
|
|
|
| Commodity Action Level | (ppb) |
| Finishing (feedlot) beef cattle | 300 |
| Finishing swine of 100 pounds or greater | 200 |
| Breeding beef cattle, breeding swine, or mature poultry | 100 |
| Immature animals and dairy cattle | 20 |
| For animal species or uses not otherwise specified, or when the intended use is not known | 20 |
| Human food | 20 |
|
|
|
| Source: FDA Action Levels for Aflatoxin | |
