Fusarium graminearum: The crop fungus tied to a smuggling case — what you need to know

Background

A University of Michigan plant scientist, Yunqing Jian, 33, who was arrested in June 2025 on accusations of smuggling a crop‑damaging fungus into the United States, pleaded guilty on Nov. 12, 2025, to smuggling and making false statements to the FBI. Under her plea agreement she received time served and is expected to be deported. The case renewed public attention on Fusarium graminearum — a fungus that already poses a major, ongoing threat to cereal crops.

What is Fusarium graminearum?

Fusarium graminearum is a widespread fungal plant pathogen that infects wheat, barley, corn and rice. In wheat and barley it causes Fusarium head blight (commonly called scab), which can severely reduce yield and quality. In extreme outbreaks scab can cut yields by as much as 45%.

Economic and agricultural impact

The U.S. Department of Agriculture estimates Fusarium diseases cost U.S. wheat and barley producers more than $1 billion annually. In 2024, extension and research plant pathologists estimated scab reduced the U.S. wheat crop by roughly 31 million bushels — about 2% of total production.

Health risks: the mycotoxin

The fungus produces a mycotoxin known as deoxynivalenol (DON), widely called vomitoxin. At high concentrations DON can cause vomiting; with prolonged or repeated exposure it may damage the gastrointestinal tract, weaken the immune system and affect the central nervous system. Livestock repeatedly exposed to contaminated feed can show reduced growth and reproductive problems.

The U.S. Food and Drug Administration issues advisory levels for DON: 1 part per million (ppm) for human food and 10 ppm for adult cattle and chickens. Grain elevators and processors routinely test incoming grain and can reject loads that exceed advisory levels. In some cases, cleaning can remove scabby kernels and grain with modest DON levels may be diverted to appropriate livestock uses.

Why import and movement are regulated

Because plant pathogens can introduce new, potentially more destructive strains, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA‑APHIS) regulates the importation and internal movement of plant pathogens under the Plant Protection Act of 2000. Transporting or releasing plant pathogens — even for research — requires permits; the USDA‑APHIS permitting process can take several months. These safeguards aim to prevent introduction of genetic variants not already present in the U.S.

How Fusarium spreads and infects crops

Fusarium infections typically occur during flowering, favored by rainfall and high humidity in early grain development. In the southern U.S., spring conditions often favor infection; risk then progresses northward and into Canada as crops mature. Between seasons the fungus survives on crop residues (straw, stalks, cobs) left in the field. It forms microscopic spores that can travel on wind currents and spread over long distances each season.

Management and prevention

No single tactic eliminates scab; integrated disease management is the best approach. Recommended practices include:

• Planting varieties with partial resistance to scab;
• Rotating crops to reduce residue-borne inoculum;
• Tillage or other residue management to bury or remove infected material;
• Applying fungicides at the flowering stage when infection risk is highest — timed applications can reduce disease severity, improve grain weight and lower DON contamination.

Fungicides provide partial protection and are not a cure; under very favorable environmental conditions for the fungus, disease can still occur though often at reduced intensity with fungicide use.

Early warning and prediction

Researchers are developing predictive tools to help growers time management actions. A multi‑institutional team from Kansas State University, Ohio State University and Penn State is building a scab risk model that combines historical and current weather station data with real‑time conditions to forecast areas and times of elevated risk. Extension specialists use these forecasts to advise growers on whether and when to apply fungicides.

Bottom line: Fusarium graminearum is an established, economically important pathogen in U.S. agriculture. The recent smuggling case underscores why strict permitting and surveillance exist — to prevent introduction of new strains that could worsen crop losses and mycotoxin risks.

Article adapted from reporting and expert commentary by Tom W. Allen, Mississippi State University.