A Kansas farmer is suing Monsanto Co. for gross negligence after last week’s discovery of a stand of the company’s experimental Roundup Ready genetically engineered wheat in an Oregon field caused global prices to plunge.

Farmer Ernest Barnes, who grows wheat on 1,000 acres in southwest Kansas, filed suit Monday in Morton County, alleging that “Monsanto has released GE [genetically engineered] wheat into the nongenetically modified wheat population.”

Several U.S. trading partners ban genetically modified organisms, or GMO, crops. Half of the country’s wheat crop is exported, accounting for annual revenues of $9 billion. After officials at the U.S. Department of Agriculture confirm that the Oregon wheat had come from Monsanto seed, Japan and South Korea abruptly suspended American imports.

“Monsanto has failed our nation’s wheat farmers,” Stephen Susman, a partner in Houston-based law firm Susman Godfrey LLP, said in a statement. “We believe Monsanto knew of the risks its genetically altered wheat posed, and failed to protect farmers and their crops from those risks.”