Soybean Diseases Have Impacted Iowa Harvests

Excessive rainfall has fueled fungal infections in Iowa soybean crops, threatening seed quality and germination rates.

Updated on Oct. 6, 2026 in Agriculture

Isometric editorial illustration of a stylized soybean pod, representing the impact of fungal pathogens on midwestern crop quality. — Excessive rainfall in Iowa has triggered fungal infections in soybean crops, creating significant concerns for seed viability and the upcoming 2027 planting season. AI Illustration. Upload story photo >

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Are you concerned that recent local crop disease outbreaks will increase food prices in your area?

Fungal diseases including purple seed stain and Diaporthe seed decay have appeared across Iowa soybean fields following periods of heavy rain. These conditions have delayed the 2026 harvest and raised concerns regarding seed viability for the upcoming season.

Why it matters

The development of these fungal pathogens threatens the overall quality and germination potential of Iowa soybean seeds, which may result in significant losses for local producers. Understanding the moisture thresholds and treatment options is essential for farmers managing infected crops before the next planting cycle.

Seed treatments can boost germination rates by 10% to 15% in infected lots. Experts suggest that seeds with over 20% Diaporthe infection are expected to fail, specifically when stored at moisture levels above 19%.

The players

Iowa State University Seed Lab

This facility provides agricultural testing services to farmers and researchers to determine seed quality and viability.

The details

The Diaporthe fungus infects soybean pods before spreading to the seeds, resulting in shriveled, cracked, or chalky mold growth. Dry storage conditions may help kill the fungus, and the Iowa State University Seed Lab is currently planning germination testing to help farmers identify viable seeds for the 2027 season.

Late September: Purple seed stain was observed in central Iowa fields.
2026: The ongoing soybean harvest in Iowa has been impacted by weather.
Spring: Infected seeds may exhibit lower germination or seedling blight.
February: Farmers are encouraged to conduct retesting of dry-stored seeds.
2027: The growing season for which current seeds are being prepared.

Market Landscape

This outbreak follows the established pattern of agricultural damage caused by the historical impact of fungal seed pathogens on Midwestern crop yields. The current crisis highlights the vulnerability of the local supply chain to volatile weather patterns that disrupt regional production standards.

Farmers must manage moisture levels below 19% to halt fungal growth and prevent significant seed loss. Those planning for the 2027 season should utilize laboratory testing to determine if chemical treatments are necessary to recover germination potential.

The takeaway

Producers should prioritize drying their harvested seeds to minimize fungal development before winter storage. Testing for infection rates early will help farmers make informed decisions about whether to treat or replace their stock for the next planting year.

What happens next

The Iowa State University Seed Lab will offer germination testing for seeds intended for the 2027 growing season, with retesting recommended for dry-stored seeds in February.