Class action lawsuits filed in Iowa and four other Midwest states allege that U.S. corn farmers have been damaged by Syngenta’s release of MIR 162 corn seed, also known as Agrisure Viptera, before it received approval from China, a key export market.

The lawsuits, filed on Oct. 3, were coordinated by Washington D.C.-based law firm Hausfeld LLP, along with several other co-counsel and firms in major corn-growing regions of the country.

“Syngenta’s...