Monsanto Co. filed a lawsuit yesterday against E.I. du Pont de Nemours & Co. and its Johnston-based Pioneer Hi-Bred International Inc. subsidiary for unlawful use of Monsanto’s Roundup Ready herbicide-tolerant technologies in corn and soybeans, Reuters reported.

Monsanto said in a release that seed companies, including Pioneer, have the right to sell soybeans and corn with the Roundup Ready trait. However, the lawsuit filed in a St. Louis court alleges that Pioneer has publicly said it will replace the Roundup Ready trait with its own glyphosate-tolerant Optimum GAT trait, and yet Pioneer admitted that its trait, when used alone, presents unacceptable risks to farmers. Monsanto claims that to repair these deficiencies, Pioneer is misusing the Roundup Ready trait to mask the problems, which violates Monsanto’s contract rights and U.S. patents.

“As the saying goes, imitation is the sincerest form of flattery,” said Monsanto CEO Hugh Grant in a release. “However, unlawfully taking technology is neither imitation nor flattery; it is unethical and wrong.”

DuPont responded by saying Monsanto is “stifling healthy competition.”

“We fundamentally disagree with Monsanto’s position that they can use their current trait monopoly to prevent the introduction of competitive seed products for U.S. growers,” said DuPont spokesman Dan Turner in an e-mail statement to Reuters.

Turner added that DuPont had tried to work with Monsanto “in good faith” through a mediation process that Monsanto requested.