Two US grain industry groups, whose members include the likes of Bunge and Cargill, called on Syngenta to mothball two genetically modified corn seed varieties, for fear of "serious economic harm" stemming from further trade hiccups with China.
The National Grain and Feed Association and North American Export Grain Association said they had sent a joint letter to Syngenta asking the company "to immediately halt commercialisation" in the US of its Agrisure Viptera and Agrisure Duracade corn seed.
The request follows the rejection by Chinese authorities, which have yet to give either variety the all clear, of more than 600,000 tonnes in imports of US corn containing Viptera, on grounds that it is as yet unapproved.
Duracade is planned for launch in the US this year.
For Syngenta to continue offering the varieties would - until they do win Chinese approval - threaten "numerous negative consequences", including cutting demand for US crops, shutting off US producers' access to some export markets, and exposing merchants to financial losses because of cargo rejections, the associations said.
The Washington DC-based groups said that they were "gravely concerned about the serious economic harm to exporters, grain handlers and, ultimately, agricultural producers… that has resulted from Syngenta's current approach to stewardship of Viptera".
"Further, the same concerns now transcend to Syngenta's intended product launch plans for Duracade, which risk repeating and extending the damage.
"Immediate action is required by Syngenta to halt such damage."
Agrimoney.com is awaiting a comment from Syngenta on the issue.
The National Grain and Feed Association claims to represent more than 1,000 companies, which handle more than 70% of US grains and oilseeds.
Members of the North American Export Grain Association include agribusiness giants such as Archer Daniels Midland, Glencore and Louis Dreyfus.
The National Corn Growers Association farmers' group on Wednesday advised members to "examine the traits approved in export markets prior to planting", but did not mention any unapproved varieties by name.
"With current gaps in trait approvals abroad, farmers should make well-informed planting decisions to avoid potentially difficult situations should elevators again decide not to accept corn with these traits at harvest," the association said.
Some elevators have declined to accept Viptera corn, because of the China trade hiccups.