What Happens In The Field, Can Follow You To The Bins
When preparing for harvest season, it’s important to understand how growing conditions can affect your crops after harvest. Factors such as fungi, mold, and environmental stress can impact storage life, grain quality, and overall crop condition during and after harvest.
Corn
Fungi and Molds
Aspergillus: Thrives in hot, dry conditions and can produce aflatoxin, which can greatly reduce grain value. If moisture is too high during storage, affected grain can continue to respire, heat, and decay.
Fusarium: Often develops before harvest and can produce fumonisins. Fusarium can spread quickly in damp grain, increasing dry matter loss and reducing nutritional value during storage.
Gibberella: Develops on corn ears under cool, wet conditions and can cause ear loss in the field. It may also produce toxins such as DON and zearalenone, which can reduce grain quality and stability during storage.
These fungi can significantly shorten storage life. When high-moisture grain is placed in storage, field molds can continue to grow, generate heat, damage kernels, and produce mycotoxins that reduce grain quality.
Environmental Stresses
Drought and heat: Stress during pollination and grain fill can reduce starch accumulation, resulting in lightweight or shriveled kernels and causing plants to mature too early.
Excess moisture and humidity: Wet conditions late in the season can encourage field fungi, ear rot, and mycotoxin development before harvest.
Early frost or freeze: A freeze before the grain reaches black layer can stop grain filling, leaving immature, high-moisture kernels with weak seed coats that are more likely to crack.
These stresses can reduce post-harvest storage life by increasing kernel breakage, speeding up mold and fungal growth, and reducing the amount of time grain can be safely stored.
Soybeans
Fungi and Seed Diseases
Diaporthe/Phomopsis: Can cause shriveled, chalky, or white-molded seeds, reducing test weight and oil quality.
Cercospora (Purple Seed Stain): Causes pink or purple discoloration on the seed coat and can reduce seed vigor.
Alternaria and Fusarium: Can remain on the seed coat following infections throughout the growing season. These fungi can accelerate seed decay when moisture is present.
Colletotrichum (Anthracnose): Thrives in warm, wet, and humid conditions and can result in moldy, discolored, or shriveled seeds.
These fungi can reduce soybean storage life by lowering seed vigor and germination, increasing respiration and heating, and making the seeds more vulnerable to storage molds.
Molds
Aspergillus: Thrives in warm, humid conditions and can cause rapid seed discoloration and quality loss.
Fusarium: Can cause shriveled, discolored, or blotchy seeds during wet conditions and reduce seed vigor.
Penicillium: Develops under high-humidity conditions, accelerating decay and reducing germination potential.
White Mold (Sclerotinia sclerotiorum): Infected seeds and sclerotia can be harvested with the crop. This can introduce high-moisture material and foreign matter into storage bins, creating potential hotspots.
Soybeans can be especially sensitive to moisture and mold-related heating during storage. These molds can increase moisture damage, encourage heating, and shorten storage life.
Environmental Stresses
Drought and extreme heat: Stress during pod fill can cause early maturity, resulting in shriveled, lightweight, and brittle seeds. Brittle seeds are more likely to develop small cracks during harvest and handling, increasing the risk of decay.
Pre-harvest wet and dry cycles: Repeated rain and dry periods can cause mature pods to swell and shrink. This can lead to pod splitting, field sprouting, and weathered seed coats that allow storage molds to enter.
Late-season frost: A premature frost during the later reproductive stages can kill plant tissue, stop natural drydown, and trap moisture in the seed. This can increase free fatty acids, reduce market grade, and decrease storability.
These stresses shorten soybean storage life by weakening the seed's natural defenses and increasing the risk of heating, respiration, oil breakdown, mold growth, and handling damage.
Wheat and Small Grains
Fungi and Molds
Fusarium: Can cause Fusarium head blight and root rot, reducing grain quality and potentially producing harmful mycotoxins.
Alternaria and Cladosporium: Can contribute to sooty head molds on mature or delayed-harvest grain, especially during wet weather.
These fungi and molds can shorten storage life by weakening the grain, accelerating deterioration, and creating conditions that allow storage molds to become established.
Environmental Stresses
Drought and heat: High temperatures during grain fill can produce shriveled, lightweight kernels with lower test weight and reduced structural strength.
Excess rain and humidity: Wet conditions near harvest can cause pre-harvest sprouting, which damages starch and weakens kernel quality.
Fungal infections: Wet and humid conditions can encourage Fusarium head blight and other field molds, leaving behind mycotoxins and weakened grain.
Hail and wind: Physical damage can bruise or crack the outer seed coat, creating entry points for fungi.
These environmental stresses can reduce the storage life of wheat and other small grains by increasing kernel damage, introducing fungal spores, and leaving grain more vulnerable to spoilage during storage.
Overall Impact on Storage
Conditions during the growing season can have a major effect on how well grain stores after harvest. Fungi, molds, moisture, temperature, and environmental stress can weaken kernels and seeds before they ever reach the bin. Identifying these risks early can help producers make better decisions about harvest timing, grain moisture, drying, and storage management.
For more information check out these sources:
Corn
Iowa State University — Aflatoxins in Corn — Excellent source for Aspergillus, drought/heat, aflatoxin, kernel moisture, early frost, and storage management.
Iowa State University — Mycotoxins and Deterioration in the 2018 Corn Crop — Excellent source for Fusarium, fumonisin, DON, zearalenone, wet grain, storage life, and damaged kernels.
Iowa State University — Aspergillus Ear Rot and Aflatoxin Production — Strong source for hot/dry conditions and aflatoxin development.
Iowa State University — Risk of Mycotoxins Associated with Hail Damaged Corn — Strong source for Gibberella, cool/wet conditions, DON, and zearalenone.
University of Minnesota — Corn Ear Rots and Mycotoxins — Useful current reference covering Aspergillus, Fusarium, and other ear rots.
Penn State Extension — Ear Rots in Your Corn Crop — Useful for post-harvest handling, drying, mold growth, and toxin management.
Soybeans
University of Minnesota — Soybean Harvest and Storage — Excellent for wet conditions, fungal pathogens, pod shatter, and harvest delays.
University of Minnesota — Soybean Seed Quality — Good general source for harvest moisture, cracking/splitting, and storage quality.
Nebraska Extension — Pod and Stem Blight of Soybean — Excellent for Diaporthe/Phomopsis seed decay.
Iowa State University — Should You Use a Fungicidal Seed Treatment on Low-Quality Soybean Seed? — Excellent source for Diaporthe, shriveled/chalky seed, germination, test weight, oil content, and wet-weather effects.
Nebraska Extension — Purple Seed Stain — Excellent source for Cercospora symptoms, germination, oil content, and marketability.
Nebraska Extension — Anthracnose in Soybean — Source for Colletotrichum.
Iowa State University — Storing Soybean — Strong source for soybean storage moisture, heating, spoilage, and germination.
Penn State Extension — Cleaning and Storage of Oilseed — Useful general source for mold, heating, foreign material, and oilseed storage.
Wheat and small grains
Nebraska Extension — Black Point and Sooty Mold in Wheat — Excellent source for Alternaria, Cladosporium, wet weather, black point, and sooty mold.
Nebraska Extension — Wheat Disease Identification — Good source for sooty head molds and repeated rain/delayed harvest.
South Dakota State University Extension — Sooty Mold in Wheat — Current source for stress, premature crop death, wet weather, and timely harvest.
University of Minnesota — Storing Wheat and Barley — Strong source for mold, storage temperature, fines, heating, and storage management.
South Dakota State University — 2026 Pest Management Guides — Current wheat disease-management reference.
Have you experienced any of these factors in your crops? We would love to hear your feedback in the comments!
