DES MOINES, Iowa

Farmers and farm businesses in 20 states have now filed more than 360 lawsuits against agricultural chemicals-maker Syngenta, and hundreds more may be coming as a federal judge organizes the complex case so they can move forward.

The dispute centers around Syngenta’s sale of a corn seed called Agrisure Viptera, which was genetically altered to contain a protein that kills corn-eating bugs such as earworms and cutworms. The U.S. Department of Agriculture approved it in 2010, and Syngenta first sold it to farmers in 2011.

China, a growing importer of U.S. corn that refuses to buy genetically modified crops it hasn’t tested, had not approved Viptera when Syngenta began selling it. In November 2013, China discovered the Viptera corn trait in several U.S. shipments.

It began rejecting U.S. corn imports in February 2014. The lawsuits say it rejected more than 131 million bushels.

Loss of revenue to the U.S. corn industry has been estimated by the National Grain and Feed Association, a trade group, at between $1 billion and $3 billion. Farmers who did not plant the Syngenta seed, grain handlers and exporters claim they lost money because of the Chinese boycott of U.S. corn and corn byproducts.

“Knowing that contamination of Viptera corn with the rest of the U.S. corn supply was inevitable, Syngenta nevertheless gambled U.S. farmers’ livelihood on approval of Viptera by the major corn-importing countries,” according to a lawsuit filed Jan. 13 in federal court in Iowa by Thomas Land and Livestock Corp., a business in east-central Iowa.

Attorneys with law firms across the country are actively encouraging people to file lawsuits through a variety of ads. And the lawsuits filed all make similar claims. They have been filed in Kansas, as well as Illinois, Iowa, Missouri and Nebraska – and hundreds more are being prepared, attorneys say.

Some suits are from farmers represented by individual attorneys, others are class-action lawsuits. Agribusiness conglomerates such as Cargill and ADM, which export grain, also have sued, claiming their businesses suffered losses. Cargill’s estimate is more than $90 million.

A federal court panel that manages lawsuits involving large numbers of plaintiffs has assigned Senior Judge John Lungstrum in Kansas City to oversee all of the cases filed from around the country in a consolidated action.

Cargill, which said it supports development of new GMO products, claimed Syngenta began selling Viptera before obtaining import approval from major markets, which was “inconsistent with industry standards and the conduct of other biotechnology companies.”